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The Nation Expands

States Emerge


After acquiring land through treaties, purchases, and the forced removal of Indian tribes, new areas of the United States were organized into territories before they were divided into individual states. These territories often became several states.

How new territories could become states was set out in the U.S. Constitution: the territory must have a large enough population to support a state government, its people must agree to American democratic principles, and a majority of the people eligible to vote must agree to statehood.

As more and more states and territories entered the Union, the question arose of whether or not slavery should be permitted in these new areas. That question would ultimately be decided once and for all by the Civil War.

The United States in 1820

By 1820, the majority of organized states were in the eastern half of the country. States in New England, the Mid-Atlantic, and the Appalachian Highlands had reached their present-day shape and size. The Southeast (with the exception of Florida) and portions of the Midwest had also largely been organized into states.
Map of states in 1820

The United States in 1850

By 1850, the United States had expanded far to the west of the Mississippi River. The discovery of gold in California — which for a time was cut off from the other states by thousands of miles — brought thousands of settlers to the Pacific Coast, and as a result of its exploding population and economy, it became a state in 1850. During the 1840s and 1850s, thousands of additional settlers traveled the Oregon Trail and settled in Oregon Country.
Map of states in 1850

The United States in the 1860s

Years of ongoing disputes about slavery, the expansion of slavery into new states and territories, and the rights of individual states led to the outbreak of the Civil War in 1861. Eleven states — Texas, Louisiana, Arkansas, Tennessee, Alabama, Mississippi, Florida, North Carolina, South Carolina, Virginia, and Georgia — seceded from the United States of America and formed a new country, known as the Confederate States of America. During the war, the United States became known as the "Union" and the Confederate states became known as the "Confederacy." In 1863, in the midst of the Civil War, a portion of Virginia seceded from the state of Virginia and became the present-day state of West Virginia.

After four long and bloody years, the Civil War ended in 1865 when the Confederacy surrendered to the Union. The Confederate States of America ceased to exist, and the states in the Confederacy became a part of the United States once more. Slavery, which had been abolished in 1863 by Abraham Lincoln's Emancipation Proclamation, also ceased to exist within the United States.
Map of states in the 1860s

The United States in 1880

By 1880, 15 years after the Civil War, many of the present-day states had been organized. In 1867, Alaska, and what is now the state of Oklahoma, remained "unorganized" territories, without territorial governments (which later became state governments).

In 1880, the territories remaining in the continental United States were largely in the Mountain States, the Southwest, and the northernmost portions of the Great Plains. Unlike most of the other territories that became individual states, Dakota Territory became two states: North and South Dakota.
Map of states in 1880

The United States in 1920

In the late 1880s and 1890s, several former territories became states. In 1889 alone, North Dakota, South Dakota, Montana, and Washington all became states. The 1890s saw the addition of Idaho, Wyoming, and Utah.

In 1898, the United States annexed Hawaii, and it became the Hawaii Territory. In 1912, Alaska became the organized Alaska Territory.

Two states in the desert Southwest — Arizona and New Mexico — joined the Union in 1912.
Map of states in 1920

The United States in 1960

In 1959, the United States added two more states to the Union: Alaska and Hawaii, the non-contiguous states. Alaska was admitted to the Union on January 3, 1959, becoming the 49th state, and Hawaii joined on August 21, 1959, becoming the 50th state.

No additional states have joined the United States since 1959. However, the United States currently has several organized and unorganized territories and commonwealths around the world, including Puerto Rico, Guam, and the U.S. Virgin Islands.
Map of states in 1960
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