How Do New States Become Part of the U.S.?

In 1783, King George III signed the Treaty of Paris, officially ending the American War of Independence and recognizing the 13 former British colonies — New Hampshire, Massachusetts Bay, Rhode Island, Connecticut, New York, New Jersey, Pennsylvania, Delaware, Maryland, Virginia, North Carolina, South Carolina and Georgia — as "free sovereign and independent states" [source: National Archives].

As part of the Treaty of Paris, England handed over the area that is now the eastern United States, from the Atlantic Ocean all the way to the Mississippi River, bound by Canada to the north and the Spanish colonies of East and West Florida to the south [source: National Atlas]. This territory far exceeded the original boundaries of the 13 colonies. In an effort to avoid territorial disputes among the new states, Congress convinced the states to relinquish control of uninhabited lands to the federal government.

These "unappropriated" frontier lands were divided into territories with names like the Northwest Territory, Mississippi Territory and Southwest Territory. One by one, portions of those territories petitioned for statehood, which is how the Northwest Territory eventually became the states of Ohio, Indiana, Michigan, Illinois, Wisconsin and Minnesota.

Other states were carved out of existing states: Vermont was sliced from New York (1791); Kentucky was born from Virginia (1792); Tennessee began as the western extension of North Carolina (1796); Maine was originally part of Massachusetts (1820); and West Virginia split from Virginia in 1863 to join the Union in the Civil War [sources: National Atlas and West Virginia Archives and History].

The rest of the U.S. began as land purchased from other countries or as the spoils of war. The Louisiana Purchase (1803) is the largest and most famous, doubling the size of the nation for a price tag of $15 million [source: Library of Congress]. The U.S. also bought Alaska from Russia and Florida from Spain (but it would take more than 20 years for Florida to achieve statehood after the Adams-Onis treaty was signed in 1819).

Large portions of the American West were once Mexican territories. Texas won independence from Mexico in 1836 and was annexed by the U.S. as a state in 1845. After losing the Mexican-American War, Mexico ceded the land that would become California, Nevada, Utah, Arizona and parts of Colorado and New Mexico for $15 million [source: National Atlas].

Hawaii, the most geographically isolated state, first became a U.S. territory in 1898, after American colonists overthrew the Hawaiian kingdom in a peaceful coup [source: Hawaii Tourism Authority]. Hawaii didn't become a state until 1959, well after its critical role in triggering America's involvement in World War II.

Puerto Rico isn't the only contender for the 51st state. On the next page, we'll discuss Puerto Rico's chances and look at some of the statehood failures that came before it.

Puerto Rico is only the latest in a long line of would-be 51st states. Over the past 200 years, there have been several attempts to carve out new states from existing ones, mostly triggered by tax and budget feuds. "South California" tried to split from the more industrialized north in 1859, but Congress said no. In 1861, parts of Tennessee, Georgia and Alabama attempted to form a neutral state called Nickjack that wouldn't secede from the Union. More recently, rural "South Jersey" tried several times to split from its crowded urban north in the 1970s and '80s [source: Trinklein].

As a commonwealth, Puerto Rico is as close as you can get to being a state without getting a star on the flag. Puerto Ricans are U.S. citizens who pay and receive Social Security benefits. They cannot vote in federal elections and they don't pay federal income taxes although they do pay things like payroll taxes, Social Security taxes and more. Puerto Rico is in charge of its own internal affairs, but the U.S. controls interstate trade, foreign relations, customs, military service, immigration, agriculture, radio and TV and the postal service.

After Puerto Rican citizens passed the referendum on statehood in 2012, what were the odds that Congress would take up their cause? Not very good. Although President Obama pledged to take action if Puerto Rican citizens made their preference clear, the political timing was not in Puerto Rico's favor. Puerto Rico has a staggering 43 percent poverty rate — more than double Mississippi (19.7 percent), the current most impoverished state — and would be entitled to billions in federal spending on social programs, Medicaid and more. Since spending cuts tend to be a top congressional priority, this is a strike against Puerto Rican statehood [source: Fabian].

Puerto Rico is one of several "unincorporated territories" acquired by the U.S. through war treaties and purchases. In 1901 and 1902, the Supreme Court ruled in the so-called "Insular Cases" to afford limited constitutional rights to unincorporated territories like Puerto Rico and Guam, on the grounds that they would never likely become states [source: Helgesen].

Today, both Guam and the U.S. Virgin Islands share Puerto Rico's odd political status; their residents are U.S. citizens who cannot vote in federal elections. Guam had hopes of holding its own referendum on statehood in 2014, but never did, and the U.S. Virgin Islands have no plans for such a vote, known as a plebiscite. Puerto Rico has shown the most political interest in statehood, holding six such plebiscites since 1967.