Complex sentence: After Baton Rouge fell to the Union troops during the Civil War in 1862, Opelousas was designated the state capitol for nine months; the governor's mansion in Opelousas stands to this day.
Split into simpler sentences: After Baton Rouge fell to the Union troops during the Civil War in 1862, Opelousas was designated as the state capitol for nine months. Indeed, the governor's mansion in Opelousas stands to this day.