[Map of the United States Including Western Territories]

Scarce and important map of United States published after the end of the Mexican-American war on the cusp of the California Gold Rush.

This map, published to accompany President James Polk’s official message to Congress on the discovery of gold in California, reflects a pivotal time in American history. The Mexican-American War had just ended and the Treaty of Guadalupe-Hidalgo completely shifted the borders of the United States, linking the nation from coast to coast and ‘completing’ Manifest Destiny. California and most of New Mexico, Utah, Arizona, and Colorado changed ownership, and Texas now ran south to the Rio Grande – the largest extent of its borders. 1848 was also the year the Territory of Oregon was established, the Illinois and Michigan Canal was completed (linking the Great Lakes to the Gulf of Mexico), and gold was found outside Sutter’s Fort in modern-day Sacramento. Underlying all this progress (the focus of Polk’s address) was the constant tension between North and South over the question of slavery.

In his 1848 map, Ephraim Gilman takes stock of this impending conflict by listing in a table the combined areas of the northern and southern states, respectively. Additionally, he boldly depicts the 36°30′ parallel – the line through which slavery cannot extend north as part of the Missouri Compromise. The map also reflects the rapid growth of the United States, with a different color outlining each iterative period of expansion. Finally, a table on the left alludes to the amount of work yet to be done in organizing and settling these vast tracts of land by listing the expansive areas under each new territory.

Sources: SDSU Library; U.S. National Archives