<P> 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 Santa Fe de Nuevo 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 . </P> <P> Comparing the boundary in the Adams--Onís Treaty to the Guadalupe Hidalgo boundary, Mexico conceded about 55% of its pre-war, pre-Texas territorial claims and now has an area of 1,972,550 km2 (761,606 sq mi). </P> <P> In the United States, the 1.36 million km2 (525,000 square miles) of the area between the Adams - Onis and Guadalupe Hidalgo boundaries outside the 1,007,935 km (389,166 sq mi) claimed by the Republic of Texas is known as the Mexican Cession . That is to say, the Mexican Cession is construed not to include any territory east of the Rio Grande, while the territorial claims of the Republic of Texas included no territory west of the Rio Grande . The Mexican Cession included essentially the entirety of the former Mexican territory of Alta California, but only the western portion of Santa Fe de Nuevo Mexico, and includes all of present - day California, Nevada and Utah, most of Arizona, and western portions of New Mexico, Colorado, and Wyoming . </P> <P> Articles VIII and IX ensured safety of existing property rights of Mexican citizens living in the transferred territories . Despite assurances to the contrary, the property rights of Mexican citizens were often not honored by the U.S. in accordance with modifications to and interpretations of the Treaty . The U.S. also agreed to assume $3.25 million (equivalent to $91.9 million today) in debts that Mexico owed to United States citizens . </P>

Which was not part of the treaty ending the mexican american war in 1848