Conversation so far:
What racial categories were there?
Mesoamerica, in reference to the cultural area where several complex civilizations developed before the arrival of the Spanish in the sixteenth century, and Aridoamerica (or simply "The North".
What racial influences are there?
Mesoamerica was densely populated by diverse indigenous ethnic groups which, although sharing common cultural characteristics, spoke different languages and developed unique civilizations.
Who did they gain independence from?
When Mexico gained independence in 1821, the casta system was eliminated as a legal structure.

Question: What was the casta system?
Self-contained rewrite: What was the casta system in the 1800's?