Answer:
Gains:
The United States got Mexico to accept the Rio Grande as its boundary, and was also granted the northern provinces of California and New Mexico, which included mineral wealth like gold mines, and extended the US border to the Pacific Ocean.
Negative outcomes:
The newly acquired land reignited the debate over slavery between Northerners and Southerners, which would eventually lead to the American Civil War.
Step-by-step explanation:
The Mexican-American war (1846-1848) was settled by the Treaty of Guadalupe-Hidalgo, by which the United States acquired the disputed Texan territory. Despite the great economic and territorial triumph this accomplishment was, the debate over whether or not slavery would be allowed in the new territory led to an increase in the fight between Northerners and Southerners. This debate would be the key element that eventually led to the American Civil War.