The bill signed by President John Tyler authorized the annexation of the Republic of Texas, which had secured its independence from Mexico in 1836. This legislative action was rooted in the United States' desire to expand its territory, fueled by the ideology of Manifest Destiny, which suggested that Americans were destined to expand across the continent. The Republic of Texas, encompassing an area larger than several U.S. states combined, was seen as essential for growth and development. Tyler's administration had been eager to see Texas join the Union, both for its economic prospects and for strategic reasons against potential foreign influences.

Negotiations for annexation had begun during the presidency of Martin Van Buren but stalled amidst political opposition and concerns about the implications of incorporating a slave state into the Union. However, Tyler, a proponent of the annexation, took decisive action by pushing Congress to pass the bill. His signing of the bill on this day was met with mixed reactions across the country — celebrated in the South but met with apprehension in the North due to the ongoing debates over slavery.

The bill's passage prompted heated national debates about expansionism and its consequences. After passing the Senate and House, Texas became part of the United States on December 29, 1845. This move not only expanded U.S. territory but also set the stage for the Mexican-American War by exacerbating tensions between the United States and Mexico, which still considered Texas part of its territory.