Instead, Article V of the treaty simply described the new U.S.-Mexico border. From east to west, the border consisted of the Rio Grande northwest from its mouth to the point where it strikes the southern boundary of New Mexico (roughly 32 degrees north), as shown in the Disturnell map, then due west from this point to the 110th meridian west, then north along the 110th Meridian to the Gila River and down the river to its mouth. Unlike the New Mexico segment of the boundary, which depended partly on unknown geography, in order to preclude all difficulty in tracing upon the ground the limit separating Upper from Lower California, a straight line was drawn from the mouth of the Gila to one marine league south of the southernmost point of the port of San Diego, slightly north of the previous Mexican provincial boundary at Playas de Rosarito.