Two detail maps on one lithograph sheet both showing locations of the two major opening battles of the war fought on consecutive days near each other in Mexican territories (present-day south Texas): Palo Alto and the Resaca de Guerrero (known to the Americans as Resaca de la Palma). The top map shows the battlefield of Palo Alto with the locations of Mexican and American troops during the battle on May 8, 1846. The bottom map is a close-up of the Resaca de Guerrero, showing Mexican positions on May 9, 1846. These maps share a common legend explaining military movements and they both have the "Camino de Matamoros" (or road to Matamoros) crossing through the centers of the maps. On both occasions Mexican forces under General Mariano Arista attempted unsuccessfully to block the road to prevent the main American force under General Zachary Taylor (marching from the port of Brazos Santiago) from relieving the small garrison that Taylor had left back at Fort Texas (later renamed Fort Brown) on the Rio Grande opposite Matamoros.
