Guamanians are U.S. citizens but cannot vote in U.S. elections. Guam's permanent inhabitants are predominantly of native Chamorro stock (37%) or Filipino descent (26%); the rest of the population mainly consists of other Pacific Islanders, Caucasians, and other persons of Asian descent. The people are overwhelmingly Roman Catholic. English, Chamorro, and Philippine languages are the main languages; efforts to preserve the Chamorro language began in the 1990s. Some one fourth of the population consists of U.S. military personnel and their dependents.

Providing goods and services for the huge U.S. bases is the major industry. Tourism, especially from Japan, is also important, and the territorial government is a significant employer. There is some light industry, and Guam is an important transshipment center for Micronesia and other Pacific islands. Some inhabitants practice subsistence farming, but large-scale agriculture is no longer possible because military installations occupy so much land. Local leaders began pressing for access to military land in the 1990s, and several facilities have been turned over.

Guam is governed under the 1950 Organic Act of Guam. The president of the United States is the head of state. The government is headed by a governor, who is popularly elected for a four-year term and is eligible for a second term. Members of the unicameral 15-seat Legislature are popularly elected for two-year terms. Guam also is represented in the U.S. House of Representatives by an elected nonvoting delegate.

Human artifacts dating from c.1500 B.C. have been found on Guam, but the first settlement may have occurred as much as 500 or more years earlier. Visited in 1521 by Ferdinand Magellan, Guam was claimed and controlled by Spain until 1898, when it was taken by the United States in the Spanish-American War. After 1917, Guam, under the Dept. of the Navy, was governed by a naval officer who was advised by a local congress. Guam was captured by Japan in 1941, was retaken by U.S. forces in 1944, and became a major base for assaults on the Japanese mainland.

The Organic Act of 1950 transferred jurisdiction to the Dept. of the Interior. During the Vietnam War in the 1960s Guam was an important base for air assaults. The island's military installations remain strategically important to the United States and are undergoing an expansion in the early 21st cent., with units being transferred there from Okinawa and other locations.

In 1969 voters rejected unification with the Northern Marianas. Since 1970 the governor has been popularly elected. Guamanians voted in 1987 to seek commonwealth status from the United States. Guam was devastated by typhoons in 1976 and 1992 and suffered a severe earthquake in 1993. Felix Camacho was elected governor in 2002, succeeding Carl T. C. Gutierrez; he was reelected in 2006.