Two hundred Texans looking for a fight answered the call of Gen. William Walker and sailed for Nicaragua on Sept. 8, 1856.

By the mid-1800s, the South was caught between the proverbial rock and a hard place. To satisfy the increasing demand for cotton, planters from Texas to Virginia desperately needed more field hands. But a strong back sold on the auction block for as much as $1,500, a price only the wealthiest plantation owners could afford.

Texans, who had argued for years over the slavery iss...