During the spring expedition to Montana, one of Hornaday's crew had captured a live male buffalo calf. Hornaday had long been interested in exhibiting live animals at the National Museum and decided to bring the calf back to the Smithsonian, where he was penned up on the lawn of the National Museum, today the Arts and Industries Building. Named Sandy for his yellowish-blond color, the calf remained in his enclosure during the summer months of 1886.
Over the course of a few weeks, however, Sandy began to acquire a humped back, more bulk and increasingly unruly tendencies. Andrew, Sandy's human attendant, had to cope with the fat and fractious animal. In 1887, Hornaday described the violent confrontations between animal captive and human keeper in the Cosmopolitan magazine: "Going up to the now quite demure looking calf...[Andrew] muttered, ‘Confound your hide! You son of a gun, if I wasn't so attached to ye, I'd kick the stuffing out o' ye right now!'"
A few days later the calf died, probably from eating too much damp clover. Hornaday eventually decided to incorporate Sandy into the unfinished group, draping his treated hide over a wood-and-clay form.
Before Sandy's untimely death, Smithsonian visitors had enjoyed watching the calf's daily activities through the fence of his pen near the National Museum. Inspired partly by this interest, Hornaday returned to another project, the establishment of the Department of Living Animals at the Smithsonian.
In October 1887, Director Goode implemented Hornaday's proposal on a trial basis, naming Hornaday the department's first curator. Goode and Hornaday justified the department's existence on the grounds that it would afford museum taxidermists an opportunity to observe the habits and positions of the various species as they were in life.
In December 1887, the initial collection of live North American mammals and birds moved into its quarters by the National Museum building. When the mini-menagerie was opened to the public, it was instantly popular with young and old alike. By April 1888, the collection had grown to 172 creatures. Hornaday admitted to the Washington Star that he hoped to establish a full-fledged national zoo for the conservation and study of wild animals sacred to the national heritage. He wanted living as well as dead buffalo preserved for posterity, arguing that preservation of a living herd in captivity would atone partially for America's extermination of the species.
In 1888, Hornaday and Smithsonian Secretary Samuel Langley drafted the zoological park proposal and forwarded it to congressional sponsors. The bill finally passed in 1889. Said a sponsor, Senator James Beck of Kentucky, "It is the duty of the National Government to secure a herd of American bison, and preserve it under the best conditions."
The legislation established the Zoological Park Commission to oversee the park's construction. Langley named Hornaday as temporary superintendent. Through donation, the Zoo soon acquired six buffalo, the first living buffalo specimens to be the property of the U.S. government. Their preservation as a living display exemplified the zoological park ideal that would guide American zoological gardens for the next half-century.
Since Hornaday's era, the number of buffalo on American soil has skyrocketed, thanks to his efforts and others. In 1902, twenty-one captive bison and 23 wild animals in Yellowstone National Park formed the nucleus of the herd of about 2,500 that survives there today. Meanwhile, other herds throughout North America, including protected herds and livestock animals on ranches, bring the total number of bison to about 250,000 animals. To some extent, all, in the United States at least, owe their survival to Hornaday.
Hornaday's Buffalo Group remained on display at the Smithsonian for almost 70 years after its first unveiling in 1888. From 1911 until 1957, the Buffalo Group stood on the first floor of what is today the National Museum of Natural History, across the Mall from its original location. In 1955, the Natural History museum's mammals division began its mid-century modernization project. By the 1940s, dioramas — displays that included painted composite backgrounds behind mounted animals and accessories — proliferated in North American natural history museums. For the modernization project, the mammal curators hoped to update the displays of the larger North American quadrupeds. The Buffalo Group would have to go, even though it contained the last wild buffalo. Not only did the Buffalo Group seem old-fashioned by the mid-20th century but the skins had not been mounted to the standards of 1950s taxidermists, who used hollow plaster-and-burlap molds rather than Hornaday's wood-and-clay forms.