Umana collected additional soldiers and servants in Santa Barbara, Chihuahua, the northernmost settlement of New Spain, and the expedition journeyed north to New Mexico.
The expedition of Humana and his partner, Francisco Leyba de Bonilla (also reported in the literature as Umana and Leyva), was carried out without the permission of Spanish authorities.
Humana and Lebya left New Mexico, probably in 1595, to explore eastwards, presumably in search of large cities and rich kingdoms rumored to be just over the horizon.
Their route from San Ildefonso led them by the pueblo at Pecos, New Mexico, and out onto the Great Plains of what is today Texas, where they met the Apache.
Gutierrez said they found abundant water in many marshes, springs, and arroyos, as well as great numbers of plum trees and nuts.
After spending an afternoon and morning apparently writing up his account of the dispute, Humana called Leyba to his tent and stabbed him to death with a butcher knife.
By this time, Oñate and a large group of settlers had arrived in New Mexico, and Gutierrez took up residence at the San Juan Bautista Pueblo.
[3] On September 15, 1599, Sergeant Major Vicente de Zaldivar Mendoza led a group of about 60 soldiers east to the Great Plains from New Mexico.
However, Zaldivar procured a quantity of dried meat, and after exploring more of eastern New Mexico, near the present day border with Texas, he returned to the Spanish settlements, arriving November 8, 1599.
In 1601, Juan de Oñate, the founder of New Mexico and governor of the new colony, led a large expedition to the Great Plains, relying on Gutierrez as a guide.
Upon reaching Oklahoma, they encountered sand dunes that made the passage of their oxcarts difficult, so Oñate chose to turn north away from the Canadian to journey onward to the "Great Settlement.
[7] Intriguing in Gutierrez's account of the Umana and Leyba expedition is the mention of a large river found about ten days north of the Great Settlement.
What does not fit very well with this possible route is Gutierrez's comment that three days beyond the Great Settlement they came upon "such a multitude of buffalo that the plain - which was level, for there are no mountains -- was so covered with them that they were startled and amazed at the sight."
If the Great Settlement were at Wichita or Arkansas City, three days travel toward the Missouri River would place the expedition in the rocky and rolling Flint Hills, not a plain.
The Platte River in Nebraska has also been suggested, but that would require a major recalculation of the route of Humana, Leyba, and Oñate as well as the location of the Great Settlement.