The Florida Parishes of Louisiana were not part of the Louisiana Purchase and, because of their strategic significance, remained within the Spanish Empire. In 1810 residents began an armed insurrection called the West Florida Revolt. After capturing the Spanish fort at Baton Rouge on September 23, 1810, the rebels raised the flag of the original Lone Star Republic and sent an army to secure their control as far east as the Pearl River. Many residents of Tangipahoa and nearby areas, who held large Spanish land grants and feared American annexation, supported Spain. A civil war developed within the Revolution, pitting Spanish loyalists against the rebels. In December 1810, American troops under William C.C. Claiborne forcibly annexed West Florida to the United States, ending the short-lived Republic of West Florida.