By RUSSELL CONTRERAS, Associated Press HOUSTON (AP) — While researching U.S. Civil War history in South Texas, Roseann Bacha-Garza came across the two unique families of the Jacksons and the Webbers living along the Rio Grande. White men headed both families. Both of their wives were Black, emancipated slaves. But Bacha-Garza, a historian, wondered what they were doing there in the mid-1800s. As she