1804

Under order of President Thomas Jefferson, the Lewis and Clark Expedition depart from St. Louis, Mo., on May 14, to map a course to the Pacific Ocean

1841

First emigrant wagon train for California. Forty-seven people leave Independence, Mo., on May 1, and reach California on November 4.

1846

After reiterated menaces, Mexico has passed the boundary of the United States, has invaded our territory and shed American blood upon the American Soil. She has proclaimed that hostilities have commenced, and that the two nations are at war. 

1847

After violent clashes with settlers over polygamy, Mormons leave Nauvoo, Ill., and head for the West under Brigham Young. They eventually settle at Salt Lake City, Utah.

1848.

Gold discovered January 24 in California.

1849

80,000 prospectors immigrate to California to follow the gold boom.

1859

First commercially productive oil well drilled near Titusville, Pa. by Edwin Drake on August 27; led to expansion of oil fields in the southwest territories.

1861

First transcontinental telegraph line completed October 24

1862

Homestead Act was approved on May 20, grants free family farms to settlers.

1867

The Grange was organized December 4 to protect farmers interests.

1869

Transcontinental railroad completed; golden spike driven at Promontory, Utah, May 10, marking the junction of Central Pacific and Union Pacific railways.