In 1838, he worked as a banker in France and sought to secure a loan for the young Republic of Texas.

They traveled to Texas from 1843 to 1847 and settled in the Medina River valley, just west of San Antonio.

The city of Castroville on the Medina River is named for him, as is Castro County in the Texas Panhandle.

[2] On February 15, 1842, Castro, in temporary partnership with Jean Jassaud, was issued two land grants by the Republic of Texas.

He made it to San Antonio in July 1844 to meet with the colonists and was escorted by the Texas Rangers to inspect his land grant.

A grant covering 3,878,000 acres over 5,000 square miles went to Henry Francis Fisher and Burchard Miller.

On June 7, 1842, Fisher[6] and Miller[7] received a colonization land grant to settle 1,000 immigrant families of German, Dutch, Swiss, Danish, Swedish, and Norwegian ancestry.