(Excerpted from Conservapedia.com)
In 1803, French emperor Napoleon Bonaparte took advantage of a lull in his war with Great Britain to sell the Louisiana Territory to the United States, more than doubling the nation's land area. This territory would later be organized as the states of Minnesota, North Dakota, South Dakota, Montana, Wyoming, Nebraska, Iowa, Missouri, Arkansas, Kansas, Oklahoma, and Louisiana proper. President Jefferson commissioned Lewis and Clark to explore the new territory, which they did from 1802 to 1804.
Florida and Texas joined the United States as a result of revolutions by settlers from the United States against their central governments. Florida's was fought in 1810, while the much better remembered Texas Revolution was fought in 1836. While Spain was willing to cut its losses in Florida and relinquished any claims on the state in the Adams-Oniz Agreement of 1819, one of the successors to its empire in the Americas, Mexico, was considerably more attached to Texas and fought the Mexican War between 1846 and 1848 to reverse its annexation by the United States. Losing badly, Mexico was forced to cede the sparsely populated northern portion of itself under the Treaty of Guadalupe Hidalgo. This territory eventually became the states of California, Nevada, Utah, Colorado, New Mexico and Arizona. At approximately the same time, President James K. Polk had agreed with the British that the 49th Parallel (degree of latitude) would serve as the boundary between the U. S. and Canada from Lake of the Woods (partially in Minnesota) to the Pacific Ocean. This territory was later organized as the states of Washington, Oregon and Idaho.
In 1867, Secretary of State William Seward purchased Alaska from Russia. Critics referred to this as "Seward's Folly." Alaska is the westernmost extremity of North America bounded on the east by Canada, on the south by the Pacific Ocean, on the west by the Bering Strait and on the north by the Arctic Ocean. At $7,000,000, Alaska cost the United States considerably less per acre than the Mexican Cession and slightly less than the Louisiana Territory. Of course, inflation was less of a factor at this time due to the world economy still being principally agrarian. Although at the time it was considered a foolish bargain, Alaska would later become a large source of economic prosperity due to large gold, oil, and other natural resources. Alaska would not be admitted as a state until 1959.