The Selective Service Act established the first peacetime conscription in United States history. The Act passed the U.S. Congress on May 18, 1917 and gave the President the power to draft soldiers. The Selective Service Act required that men between the ages 21 and 30 register with local draft boards. (The age range was later changed to 18-45.)

In his war message on April 2, 1917 President Woodrow Wilson pledged all the nation's "material resources" to the Allied war effort. But what the Allies most urgently needed were fresh troops. Few Americans, however, rushed to volunteer for military service.

By the end of WWI, some 24 million men had registered, and some 2.8 million had been drafted. In fact, more than half of the almost 4.8 million Americans who served in the armed forces were drafted.

The draft began in November 1940, a year before the United States formally entered World War II. In 1918, the U.S. Supreme Court rendered its opinion that conscription was not considered involuntary servitude under the Thirteenth Amendment, but rather part of Congress's right to raise and support armies. It also ruled that government censoring individuals from urging individuals to resist a draft was not a violation of the Constitutional guarantee to "free speech" found in the First Amendment.

Though the United States halted conscription in 1973, the Selective Service remains as a means to register American males upon reaching the age of 18 as a contingency should the measure be reintroduced.

See also: Conscription in the United States