When William John McGee set out from Washington, D.C., for the Sonoran Desert in 1894, he was inspired by a passion for adventure as much as a thirst for knowledge. McGee lived in an era when discovery was made through travel rather than study, and reputations were forged by going where no outsiders had gone before. A self-taught scientist in the newly forming field of anthropology, McGee led two expeditions through southern Arizona and northern Sonora for the Bureau of American Ethnology. There he conducted ethnographic research among the Papagos (Tohono O'odham) and the Seris, and his subsequent publication The Seri Indians helped secure his place in the anthropological community. McGee's complete journals of the expeditions, kept in small field notebooks and preserved in the Library of Congress, are published here for the first time. These journals contain detailed descriptions of the country and people McGee encountered and convey the adventure of traveling through wild and unfamiliar places--including a voyage to Isla Tibur—n, or Shark Island, in the Gulf of California--and being plagued by foul weather, a shortage of supplies, and fear of attack from hostile Indians. Trails to Tibur—n features 57 historical photographs taken on the expedition, capturing the places McGee saw and the people he encountered. Fontana's notes to the diary provide useful botanical, geological, and ethnographic information, while his introduction places McGee and his field work in the context of late-nineteenth-century anthropology and science. Trails to Tibur—n reveals McGee's versatility as a field worker and shows his methods, often questioned today, to be the reasonable response of a man caught up in the intellectual fervor of his time. For anyone wanting to share in the spirit of adventure, these journals are a landmark in the annals of exploration.