Manuel Castellanos was a Franciscan priest assigned to the College of Santa Cruz de Querétaro. Father Castellanos, along with Francisco Hidalgo and three other missionaries, left the college on January 21, 1716, for Saltillo. There they joined the expedition of Domingo Ramón, charged with reestablishing the Spanish presence in East Texas. On April 16 the contingent of priests reached San Juan Bautista, where they were reunited with three additional brethren of the college. On April 27, 1716, Castellanos left the gateway mission as a member of the Ramón expedition. En route to East Texas, he narrowly escaped drowning while fording the rain-swollen Colorado River near the site of present Austin. Ramón and his followers reached the land of the Tejas Indians in late June, and on July 3 Mission San Francisco was reestablished under the name of Nuestro Padre San Francisco de los Tejas. Joining Francisco Hidalgo, who served as minister of the new mission, was Manuel Castellanos. The latter was also given responsibility for the spiritual care of the soldiers at nearby Nuestra Señora de los Dolores de los Tejas Presidio. In late 1716 Father Castellanos fell ill while ministering to soldiers of the garrison. He evidently recovered from an illness believed to have been malaria, and he apparently remained in East Texas until the Spanish withdrew to San Antonio during the course of the Chicken War.