The glowing accounts of the new discoveries made by the Rodríguez-Sánchez expedition of 1581–82 spread rapidly throughout the northern frontier of the viceroyalty of New Spain, fired imaginations, and stimulated activity. Moreover, in Santa Bárbara there was the greatest concern for the safety of Fray Agustín Rodríguez and Fray Francisco López, the two Franciscans who had remained in New Mexico to continue their missionary work. In Santa Bárbara a Franciscan named Bernardino Beltrán sought authority to send a rescue mission to New Mexico, and he began to search for a suitable leader to command the military escort. Residing in Santa Bárbara at this time was Antonio de Espejo, a wealthy fugitive from justice accused of murder, who had taken refuge on the frontier and was looking for an opportunity to exonerate himself. Espejo therefore offered his services to Fray Beltrán and agreed to join an expedition to rescue the two friars and to pay all expenses.
The Espejo-Beltrán expedition, consisting of fourteen soldiers, their servants, 115 horses and mules, arms, munitions, and provisions, left San Bartolomé, a mining outpost nine leagues north of Santa Bárbara, on November 10, 1582. A month later the expedition reached the juncture of the Río Conchos and the Rio Grande, which Espejo named the Río del Norte. Up the river was a nation Espejo called the Jumanos, who lived in large pueblos with flat roofs, gave the Spaniards food, and told them that some years before three Christians and a Negro had passed through the area. In January 1583 the expedition approached the El Paso area, inhabited by the Suma and Manso Indians. They followed the Río del Norte upstream, through a "mountain chain on each side of it, both of which were without timber," a possible reference to El Paso del Norte, as Spaniards later named it.
In late January 1583 Espejo and his companions reported "a large black rock," a possible reference to Elephant Butte, and on February 1 they arrived at the southernmost pueblos of New Mexico. Here they learned that both Rodríguez and López had been killed by the Indians. Beltrán therefore proposed that the expedition return since the fate of the two missionaries had been determined, but Espejo, whose leadership was unchallenged by this time, insisted on further explorations in the hope of finding riches. From March to July 1583 the party explored extensively in what is now Arizona. Although no riches were found, Espejo continued to be convinced that the reports of wealth were true. Meanwhile, Fray Beltrán and several others had left the expedition and returned to Santa Bárbara.
In June 1583 Espejo and his companions turned their attention eastward. They entered the Pecos valley, followed the Pecos River southward into the land of the Jumanos, and on August 22 reached the juncture of the Rio Grande and the Conchos. The little band finally arrived in San Bartolomé on September 10, 1583, after an absence of ten months.
Espejo's report of rich silver mines and natives of an advanced cultural level who would be receptive to conversion aroused widespread interest and a strong desire among Spanish officials to occupy and colonize the lands that he had visited. In the succeeding years there were numerous applicants, including Espejo, for the necessary official authorization to conquer and colonize New Mexico, but all were denied. Not until 1595 was a candidate found with the necessary qualifications to gain the approval of the Spanish crown for this important assignment. His name was Juan de Oñate.