Complex sentence: Post-war Texas grew rapidly as migrants poured into the cotton lands; they also brought or purchased enslaved African Americans, whose numbers nearly tripled in the state from 1850 to 1860, from 58,000 to 182,566.
Split into simpler sentences: Post-war Texas grew rapidly as migrants poured into the cotton lands of the state. They also brought or purchased enslaved African Americans, whose numbers nearly tripled in the state from 1850 to 1860, from 58,000 to 182,566.