As the United States expanded westward over the course of the 19th century, many new people became part of the country. The role of these new residents increased, although not without challenges. House records document these early events and the journey of Hispanic Americans in what became the Southwest United States, and in Congress.
The 500,000 square miles of land acquired by the 1848 Treaty of Guadalupe Hidalgo, which ended the Mexican-American War, was a major territorial acquisition that changed the landscape, politics, and population of the country and situated it as a dominant power in the world. On December 5, 1848, in his annual message to Congress, President James K. Polk transmitted this map as an exhibit to illustrate his desired plan for the land, including the present-day states of California, Nevada, and Utah, as well as parts of Arizona, Colorado, New Mexico, and Wyoming. The map shows the latitude of 36°30' established in the Missouri Compromise of 1820: Slavery was prohibited in the Louisiana Territory in areas north of this latitude, and Polk advocated extending the prohibition to the Pacific Ocean to cover the newly acquired acreage. The Compromise of 1850, actually a series of different bills, arose in response, resolving the status of the new territory and diffusing sectional tension over slavery for a time.
Although the Compromise of 1850 resolved the status of the new territory in terms of slavery for the moment, the nearly 2,000-mile boundary between Mexico and the United States remained largely unexplored and unmapped. Between 1848 and 1855, the U.S. Army Corps of Topographical Engineers surveyed the land under the direction of U.S. Boundary Commissioner William H. Emory. Part of their mandate was to illustrate the border between the United States and Mexico. The red line in this sketch shows the U.S.-Mexico border before the land was purchased from Mexico. The area south of the Gila River is present-day Arizona. The lengthy and extensive survey resulted in the Report on the United States and Mexican Boundary Survey, published in volumes from 1857 to 1859. The report was published as House Executive Document No. 135 during the 34th Congress. Richly illustrated with flora, fauna, and inhabitants of the region, it remains one of the foremost publications on exploration of the West.
The breakneck pace of continental expansion in the 19th century collided with the realities of governing a largely unsettled and more diverse nation. These House records document the acquisitions that affected Hispanos and how these new inhabitants came to be represented in Congress.
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