The following year Brown joined the museum staff for its first expedition to excavate dinosaur skeletons outside Medicine Bow, Wyoming. It was an unforgettable trip: For the rest of his life, Brown harbored tremendous pride in his first professional find, an enormous plant-eating dinosaur similar to, but even longer than, the then recently discovered Apatosaurus. “I was . . . fortunate in discovering a partial skeleton of . . . Diplodocus. This was the first dinosaur excavated by any American Museum expedition, and here I introduced the use of plaster of paris in excavating fossils.” At age 24 Brown had laid the cornerstone for what would become the world’s most famous collection of dinosaurs. Furthermore, by covering the 150-million-year-old hindquarters of that giant sauropod in a sturdy plaster jacket—a method that enabled him to safely ship and store the beast’s delicate remains—he helped establish a critical collecting technique that is still used by paleontologists around the world.

And Brown had barely begun. After returning from Patagonia, he discovered the first T. rex fossil, in 1902 in Hell Creek, Montana. He then traveled across the Canadian border to the Red Deer River, where, between 1910 and 1915, he excavated the sharp-toothed tyrannosaur relative Albertosaurus as well as the smaller, ostrich-shaped Struthiomimus. There he also found tanklike armored dinosaurs like Edmontonia and Euoplocephalus; elaborately crested, plant-eating duckbills, including Corythosaurus and Parasaurolophus; and fierce horned brutes like Chasmosaurus and Centrosaurus, relatives of Triceratops. These finds provided the first comprehensive look at North America’s dinosaur fauna of 75 million years ago.

Nor was Brown satisfied with simply collecting dinosaur bones. On a trip to the Greek isle of Samos from 1923 to 1924—an expedition he undertook with his intrepid second wife, Lilian—Brown hired a team of 18 men and 6 women to haul dirt in baskets for “the attractive sum of 35 drachmas (70 cents) per day for the men and 20 drachmas per day for the girls.” In the wake of the Greco–Turkish War of 1921–22, the island was inundated with Greek refugees desperate for work, so Brown did not have any difficulty finding willing workers. Their extensive quarrying generated 56 cases of spectacular fossils “representing three species of three-toed horses, rhinoceroses . . . many species of antelope and gazelle . . . birds, and a variety of carnivorous mammals.” The jewel was an exquisitely preserved skull of an early relative of giraffes, Samotherium.

The peripatetic Brown collected so many specimens on his travels that even today dozens of large boxes of his fossils have yet to be opened. Crates labeled “mammals from Samos” and “ornithomimid from Hell Creek” rest on sanitized racks in the storerooms of the American Museum of Natural History simply because there are not enough staff workers to unpack them, remove the plaster, and prepare them all. As Brown neared his 90th birthday in 1963, his successor at the museum, Edwin Colbert, marveled at how much of the museum was Brown’s single-handed work: “There are, in our Tyrannosaur Hall, 36 North American dinosaurs on display. . . . You collected 27, an unsurpassed achievement.”

For all of Brown’s success as a collector, his direct impact as a scientist was strangely modest, compromised by his time abroad and by his laxity in publishing his discoveries. The CV that he compiled for his memoirs—which he never finished—shows that there were only five years between 1897 and his retirement in 1942 in which he did not participate in a major expedition. Yet he penned few scientific papers, and those that he did publish are mostly short notes. On the other hand, his longer publications, like his monograph on Protoceratops, a Mongolian relative of the great horned dinosaurs, are classics, both for the freshness of the presentation and the quality of the analysis.

Brown’s real legacy lies with his discoveries themselves, which still serve as a foundation for numerous geologic and biological research projects in paleontology. His excavations in the Missouri Breaks—the site of the renowned T. rex burial ground in Hell Creek—yielded not only Tyrannosaurus but also the bizarre Pachycephalosaurus, whose head was topped with a 10-inch-thick crown of solid bone, and the best-known horned dinosaur, Triceratops. At the same time, Brown documented the sequence of rock layers at the site that reveal how the nonavian dinosaurs dramatically died off 65 million years ago. The lowest layer of coal marks the boundary between the underlying Hell Creek Formation, with its rich dinosaur fauna, and the younger overlying Tullock Formation, with its surviving fauna of small mouselike and shrewlike mammals. This is the world’s best record of the faunal and floral changes that occurred worldwide at the end of the age of dinosaurs and the beginning of the age of mammals.

Even now many researchers continue to prospect and probe Hell Creek’s rugged exposures for clues to the dinosaurs’ demise. In the early 1980s we helped collect rock samples from the site, which were then analyzed to identify the iridium-rich clay layer that is now understood as the fallout from the impact of a comet or asteroid. Many scientists believe this collision caused the extinction of most dinosaurs, although some still argue that immense volcanic eruptions in India may also have played a role.

Brown helped establish our contemporary view that not all dinosaurs are extinct--some of them fly about today in our backyards.

Ironically, Brown also gathered key fossil evidence establishing that, in reality, not all dinosaurs went extinct at the end of the Cretaceous. During the 1930s, in the badlands of southern Montana’s Crow Indian Reservation, Brown discovered a diminutive carnivorous dinosaur now named Deinonychus. Because skeletons of such small carnivores were extremely rare, he immediately recognized its importance and began describing it in a scientific paper. Brown’s illustrations indicate that he clearly comprehended this animal’s birdlike characteristics. He never finished his study, however, and until 1960 the specimen languished in a drawer labeled Daptosaurus, the name he intended to give the new animal.

A student named John Ostrom picked up where Brown left off, renaming the specimen and rejuvenating the century-old debate about the evolutionary origin of birds. Subsequent research led to the radical but now widely accepted conclusion that birds are, in fact, the only living descendants of dinosaurs. Thus Brown helped establish our contemporary view that not all dinosaurs are extinct—some fly about in our backyards.

Brown’s succession of exotic discoveries made him one of the greatest scientific celebrities of his day. The public nicknamed him “Mr. Bones,” and one writer noted that “wherever Brown went on his expeditions in the American West . . . he was feted by the local populace. Droves of people would meet his train and vie for the honor of driving him from the station to town.” Museum archives reveal that Brown’s zest for geologic exploration inspired a second, clandestine life. From early on Brown’s expeditions for fossils had served as a smoke screen for occasional sojourns as an intelligence agent and corporate spy. During both world wars he funneled geologic knowledge gleaned from his fossil-hunting expeditions to the United States government. He occasionally confided in museum colleagues, as in a 1921 letter to paleontologist W. D. Matthew stating that he had “an exciting time in Turkey, and secured much desired data for the State Department.”

In 1941 the American government contacted museums to find out where their curators had done fieldwork in order to harvest information about remote and strategically vital areas. Although Brown was about to retire, he happily obliged, citing his travels to Canada, Cuba, Mexico, Patagonia, France, England, Turkey, Greece, Ethiopia, Egypt, Somalia, Arabia, India, and Burma. He also volunteered for service and was assigned to the Office of Strategic Services, the forerunner of today’s CIA, where he used his knowledge of Samos and the Aegean Islands to help plan one of the potential invasion routes into Europe. From 1943 to 1945 he was transferred to the Bureau of Economic Warfare, where his duties included “interpreting aerial photographs to detect camouflage in areas of Africa, India, Burma, and the Mediterranean Islands” as well as conducting an aerial reconnaissance of oil fields in Alberta, where he had earlier prospected for petroleum on the Duke of Windsor’s large ranch.

Because of his passion for both geology and paleontology, Brown also forged close ties with oil and mining companies. Part of the industry’s appeal was financial; he charged a consulting fee of $50 per day, almost $800 in today’s currency. These contacts could also be lucrative sources of fossil-hunting cash. In 1934, with museum funds for fieldwork in short supply, Brown approached officials of the Sinclair Oil Corporation in search of financial support. The company’s president became so enamored of Brown and his work that he personally backed Brown’s expedition to northern Wyoming, where he discovered the famous Jurassic dinosaur graveyard named Howe Quarry. To this day the Sinclair logo features an image of Diplodocus in deference to this partnership.

Brown’s expeditions for fossils served as a smoke screen for sojourns as an intelligence agent and corporate spy

Brown’s oil company contacts were extensive. In 1920 he quite likely fled a jilted lover’s lawsuit by skedaddling for Abyssinia (now Ethiopia) under the banner of the Anglo American Oil Company, an offshoot of John D. Rockefeller’s Standard Oil. His mentor, Henry Osborn, was supportive of such ventures because Brown kept his keen eyes peeled for fossils while prospecting for oil. In this way Osborn reaped the fruits of Brown’s labors while the oil company paid for them. Brown’s letters—in which he invariably addresses his supervisor as “my dear Professor Osborn”—maintain the careful guise of an eccentric fossil hunter, but they also contain carefully worded notes about both oil prospects and the activities of European diplomats, military personnel, and businessmen. Those notes also contain telling details about his targets’ wives and daughters.

Brown was quite the roué, as the museum’s archives reveal. From 1920 through 1924, his global search for fossils took him not only to Ethiopia but also to India, Indochina, and back through the Mediterranean. His correspondence from the period suggests that this marathon was in part an effort to escape the spurned woman’s legal suit against him. Upon hearing about the case, Brown anxiously wrote to his supervisors to assess the potential damage. “I’m at a loss to know how my standing at the Museum has been affected by this blackmail case and whether I shall be wanted there again,” he wrote on December 20, 1919, from Okmulgee, Oklahoma. “It seems to me best to settle the business in or out of court before I come [back] to the Museum. . . . I know what a lot of gossips there are there. . . . It is purely blackmail and I doubt if the woman would dare go to court, and yet you know how innocent parties can be humiliated . . . in such a case.”

A few notes and poems from admiring women remain in the archives, although legend has it that a loyal assistant removed most of these from Brown’s desk after his death. Brown’s roving eye was not lost on his second wife, Lilian, who in a letter to a friend compared the polygamous traditions of the East with those of the West. “After all, this is better than the Christian way of living,” she wrote. “Our men have many wives on the side, and the only thing that makes it wrong is the fact that they might be found out??????”

Lilian was apparently ready to forgive Brown some of his wanderings. As Brown’s daughter, Frances, relates in a self-published 1987 biography, Let’s Call Him Barnum, he and Lilian married in 1922 in India, where Lilian was ostensibly on a world tour with an aunt. “The more likely scenario was that she, like others before her, had decided that Barnum was the husband she wanted, and if he would not come after her, she would go after him, even if it meant crossing a couple of continents.”

Lonely, and as his daughter states, “ripe for the plucking,” more than a decade after the death of his first wife, Marion, in 1910, Brown rushed to meet Lilian in Calcutta “and quickly decided to make her his wife.” Lilian, no doubt, expected to be whisked away on a romantic Oriental honeymoon, but as his daughter relates, “that Barnum was not youthfully starry-eyed and glowing over this marriage” was clear from his choice of activities for the nuptial reception: “The bride and groom spent the afternoon of their wedding day in the chairs of the only two English dentists in Calcutta. To Barnum this was just a routine practicality.”

With Brown, fossils almost always came first, and Lilian quickly adapted, helping to collect and keep records in the field for her husband. Health risks were rampant: In the lowlands of Burma, Brown contracted malaria, but his wife saved his life with round-the-clock nursing until his fever broke. Their marriage lasted for 40 years, until Brown’s death in 1963, probably because Lilian possessed a streak of independence almost as wide as her husband’s. After their wedding, she set off on her own to Kashmir for a solitary honeymoon. Along the way, she caught the eye of an eminent maharaja, who lavishly entertained her and permitted her to interact with his harem—an honor not previously bestowed upon any westerner.

As colorful as Brown’s adventures were, they are now largely forgotten, while his fossil finds are more prominent than ever. His discoveries permeate the American Museum of Natural History, whether one casually strolls through the public exhibition spaces or rummages intently through the cloistered collections. When the museum renovated its fossil halls in the 1990s and its dinosaur storerooms in 2000, we faced the daunting task of conserving and moving Brown’s magnificent collection. It was humbling to see firsthand how many of the specimens that draw millions of visitors to the museum each year were unearthed through Brown’s efforts. Of the 80-odd specimens in the renovated halls, 32 were found by Brown and his field crews.

It was our special privilege to work with Brown’s most famous specimen. During the renovation, our most difficult and delicate job was to remount Brown’s T. rex by modifying its upright “Godzilla” posture into a more scientifically accurate horizontal posture. When Brown and Osborn originally designed their upright mount, they built a one-sixth scale model of the skeleton, with each bone carved out of wood, and then mounted it on a wire framework. We reworked the same model to realign the posture for our new mount. Then, each immense yet fragile bone had to be lifted gently off the old armature, cleaned, conserved, and carefully repositioned on the new armature, much as Brown and his preparators had painstakingly done almost a century before. It was an emotionally draining exercise because the skeleton represents one of evolution’s most iconic specimens; its spectacular four-foot-long skull gave humanity its first face-to-face glimpse of the most imposing and ferocious predator ever to walk the continents. Our remounting took more than a dozen dedicated scientists and fossil preparators almost two years to complete, but Brown’s masterpiece will glower menacingly at new generations of entranced visitors for decades to come.

Brown’s incomparable ancient menagerie—along with a few boxes of notes and several cabinets of photos—also serves as his epitaph. Today all of Brown’s immediate family and almost all of his contemporaries are dead, and no known recordings of him exist. It is therefore impossible to know his true mind. Field portraits snapped at different periods show him progressing from a proud but youthful apprentice, sitting in a quarry with his first dinosaur find, to a bald yet dapper patriarch, confronting an outcrop in his full-length beaver-skin coat. One can see his determined face but cannot probe the thoughts inside.

Beyond a consistent willingness, or even gleeful propensity, to take calculated risks in his professional and personal life, Brown remains something of an enigma. He was a master collector who disdained recording the details of his monumental discoveries. He was a meticulous researcher who found little time for publishing his scientific insights. He was a world-renowned, New York–based scientist who seemed most at ease with strangers in field settings far from home. He was a husband who delighted in his wives’ company but felt unconstrained by conventional rules

But at least we still have one unforgettable and still tangible connection with Brown. It is extraordinarily powerful to sit in our archives, gingerly grasping the tattered, yellow, century-old letter that Brown wrote to Osborn from the badlands of Hell Creek describing humanity’s first encounter with a T. rex in 1902. Befitting of Brown, our eyes struggle to decipher his rambling scrawl, but once comprehended, the words are quite self-assured, if disarmingly simple: “Quarry No. 1 contains [several bones] of a large carnivorous dinosaur not described by Marsh. . . . I have never seen anything like it from the Cretaceous.”