Even after Mexico achieved independence from Spain in 1821, it continued to exclude non-Catholics from immigrating until the liberal Reform. After the fall of the monarchy of Agustín de Iturbide in 1823, the newly established federal republic promulgated a new law regarding immigration, the General Colonization Law. The Spanish Crown's controls over foreigners doing business in Mexico were no longer in place, and some British businessmen took an interest in silver mining in northern Mexico. The Mexican government sought to populate areas of the north as a buffer against indigenous attacks. The Mexican government gave a license to Stephen F. Austin to colonize areas in Texas, with the proviso that they be or become Catholics and learn Spanish, largely honored in the breach as more and more settlers arrived. Most settlers were from the slave-holding areas of the southern U.S. and brought their slaves with them to cultivate the rich soil of east Texas. The experiment in colonization in Texas went disastrously wrong for Mexico, with Anglo-Texans and some Mexican Texians rebelling against Mexico's central government and gaining "de facto" independence in 1836. However, Mexicans of various ideological stripes called for attracting immigrants to Mexico in the nineteenth century.