Here is a short overview on the History of The Draft (or "Conscription) up to the beginning of WWII. PBS - © 2001 MacNeil/Lehrer Productions

Colonial Period 1600s, 1700s - Each colony forms a militia made up of all adult male citizens.

Revolutionary War (1775 - 1783)- A regular army is raised by offering enlisted men cash bonuses and a promise of free western land after the war is over. When this system does not attract enough soldiers, General George Washington calls on state militias. However these local armies are made up of poorly trained citizens who often have to return home to tend to their farms.
Once he becomes president, Washington tries to register all men for service. Congress does not pass his regislation or others proposed by Presidents Adams, Jefferson, and Madison.

War of 1812 - Recruitment efforts include thirteen-month enlistment periods, a sixteen-dollar sign-up bonus and the promise of three months' pay and one hundred sixty acres of land after service.
The Congress authorizes President James Monroe to call up one hundred thousand state militia. Some states refuse.

Mexican War (1846 - 1848) - The one-year enlistment of many troops expires. Military action must wait until replacement troops arrive.

Civil War (1861 - 1865) - The Confederate Army enlists volunteer troops for one-year periods while troops for the North enlist for periods of three or nine months.
Eventually, each side turns to conscription as a means of keeping its armies in place after enlistment periods end.

North - In March 1863, Congress gives President Lincoln the authority to require draft registration by all able-bodied men between the ages of 20 and 45, regardless of their marital status or profession. Substitute soldiers are permitted to be hired and for $300.
Many northern businessmen resist service and the Governor of New York, Horatio Seymour, declares the conscription act unconstitutional.

South - The Confederacy passes their conscription law in April 1862. Three years of military service is required from all white men between the ages of 18 and 35. Substitutes are hired, resulting in poor morale and insufficient numbers of troops. Later, the age limit is extended to include men between 17 and 50, and in 1865 the Confederate Army begins to conscript slaves.

******* PEACE (31 Years) *******

1898 (Spanish-American War) - Congress declares that all males between 18 and 45 are subject to military duty.

May 1917 - Congress passes the Selective Service Act, establishing local, district, state, and territorial civilian boards to register men between the ages of 21 and 30 for service in World War One. There is much opposition.
During the first drawing, 50,000 men apply for exemptions and over 250,000 fail to register at all. In one round-up held in New York City in 1918 to catch those who failed to report, 16,000 men are arrested. After the war ends, efforts to set up standard military training and service are defeated in Congress.

1920 - The National Defense Act establishes a system of voluntary recruitment.

***** PEACE (21 Years) *****

1940 - Congress enacts the Selective Training and Service Act. All males between the ages of 21 and 35 are ordered to register for the draft and the first national lottery is held. As World War II progresses, the draft age is lowered to 18 and men are called to service not by lottery number but by age, with the oldest going first.

1941 - Following the attack on Pearl Harbor, Congress gives the president power to send draftees anywhere in the world, removing the distinctions between draftees, regulars, National Guardsmen and Reservists, and creating one army made up of all.

1973 -- "THE DRAFT (via 'SELECTIVE SERVICE') finally ends. US Military Service becomes a voluntary process