In the 1830s and 1840s, “manifest destiny,” the idea that the United States was destined to expand across the entire continent, was used to promote further territorial expansion. And the nation expanded quickly: in 1845, the United States annexed Texas; in 1846 the Oregon Treaty ended British claims to Oregon Territory; in 1848, following the Mexican-American War, Mexico ceded much of the Southwest to the United States; in 1853 the United States bought an additional tract of land from Mexico. States joined the Union at a relatively fast pace: California became a state in 1850 and Oregon in 1859, Nevada in 1864, Nebraska in 1867, Colorado in 1876, South and North Dakota, Montana, and Washington in 1889, Wyoming and Idaho in 1890, and Utah in 1896. As new towns like Denver and Phoenix sprang up in these new states, established towns and cities underwent a surge in growth to accommodate the new industries and new populations that westward expansion brought with it. This set of primary resources containing images and documents provides a window into this time period, as well as a Teacher's Guide with historical context and teaching suggestions.