Click on the different colored states to learn about each wave of admission.
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Original States
(1787-1789)
In 1803, France sold the Louisiana Territory to the United States in what was called the “Louisiana Purchase.” The president, Thomas Jefferson, sent an expedition led by Meriwether Lewis and William Clark to explore this new territory and beyond into the West. Their mission was to find a way across the continent to the Pacific Ocean, record the animals and plants they saw, and meet with American Indian tribes to make or keep peace. They set off in 1804 from St. Louis, Missouri, and returned in 1806, after 27 months of exploration. They were helped along the way by a woman from the Shoshone nation, Sacagawea. One of the members of the expedition was an enslaved African American man named York. This exploration sparked an interest in the American West and inspired the pioneers to make the dangerous journey across America in the coming years.
Second Wave
First 100 years, 1790‒1887
On April 30, 1803, Napoleon Bonaparte of France sold Thomas Jefferson, then President of the United States, 885,000 square miles of territory in North America for $15 million. Congress sent Meriwether Lewis and William Clark to find out exactly what the United States had purchased. On November 7, 1805, the Lewis and Clark expedition reached the Pacific Ocean and the way to the West was opened. Fur trappers, traders, and finally pioneer settlers followed.
President James Polk stated that it was America’s "Manifest Destiny" to settle North America from the Atlantic Ocean to the Pacific Ocean, and the people of America showed their agreement by pushing the borders of the United States across the Mississippi River and ever westward. In 1841 the first group of 69 pioneers left Missouri and headed west, bound for Oregon. From 1841 until the completion of the transcontinental railroad in 1869, more than 350,000 citizens traveled by foot and wagon to reach Oregon and California. Would slavery be allowed in the new country, including the rich gold diggings of California? The debates that followed gave rise to the Republican Party, whose triumph in 1860 sparked the Civil War.
Third Wave
After 100 years, post-1887
By 1883 several more transcontinental railroads had been built. An expanding transportation network, together with increased industrialization, hastened the transition of the United States from a rural/agricultural nation to an urban/industrial one by
the early twentieth century. As travel to the West became more efficient and trade became more profitable and people began to settle there in greater numbers, former western territories became new states. The admittance of new states tapered off after Arizona (1912), until finally, in 1959, almost 100 years after the Civil War, Alaska and Hawaii were admitted as the last of the fifty states.