Documenting the Discoveries

The Treaty of Guadalupe Hidalgo that ended the war with Mexico in 1848 added more than 525,000 square miles of western territory to the United States—an area that now encompasses all or parts of eight states. Members of Congress, recognizing the potential of this territory for settlement, fiercely debated whether or not to allow slavery there and which route a transcontinental railroad should follow through it. To inform future legislation, Congress funded a full report on the region as part of the boundary survey.