For military ancestors who served prior to World War I, the compiled military service records are a good place to start. These are basically just what they sound like — an abstract of the available military information on an individual compiled from a variety of service-related records.

Compiled military service records were originally begun in 1894 in an effort to reconstruct records of the American army and navy destroyed by fires in 1800 and 1814. The project eventually grew to cover all soldiers serving in volunteer units in wars between 1775 and 1902, including not only individuals from the American Revolution and War of 1812, but also those who served in various Indian conflicts, the Mexican War, the Civil War, the Spanish-American War, the Philippine Insurrection, and the Boxer Rebellion.

A compiled military service record consists of a card with the soldier's name, rank, and unit, along with abstracted information taken from muster rolls, hospital records, pay vouchers, record books, orders, correspondence, and other records. This card is then placed in an envelope, or jacket. Sometimes original documents may also be included in the envelope.

The compiled military service record will generally provide you with your ancestor's rank, unit, the state from which he served, the date enlisted, and the length of service. You may also find the age, residence, a physical description, and date of discharge or death.

The National Archives in Washington, D.C., is the official repository for federal military service records of personnel who served in the U.S. Army, Air Force, Navy, Marine Corps, or Coast Guard between the Revolutionary War and about 1912. This includes compiled military service records for Confederate Army soldiers.

Military service records, including compiled service records, can be ordered online, or by mail using NATF Form 86 (which you can download online). Indexes and/or digitized images of these compiled service records can also be found online.

• Fold3, in cooperation with the National Archives, offers subscription-based online access to the compiled military service records of soldiers who served in the American army during the Revolutionary War, as well as for Confederate Civil War soldiers (most of the Confederate records and some records of Union soldiers).

• Ancestry.com features an index to the compiled military service records for the volunteer soldiers who served during the War of 1812; index and images for compiled military service records for Revolutionary War soldiers; and indexes and some digitized images of Civil War service records, including those of the U.S. Colored Troops. Use the Ancestry Card Catalog to locate and search each specific database.

• The Civil War Soldiers and Sailors System (CWSS) offers a free index of more than 6 million Civil War Confederate and Union soldiers compiled from the General Index Cards of the compiled military service records at the National Archives. Click on Soldiers or Sailors on the right-hand side to search for a name.

The War Department did not compile military service records for those who served in the regular army. The place to start researching pre-World War I enlisted Army personnel online is a set of helpful records titled U.S. Army Register of Enlistments, 1798–1914 at Ancestry.com, digitized from National Archives microfilm publication M233.

U.S. Marine Corps Muster Rolls, 1798–1958 is a collection of regular lists of Marine Corps personnel that also includes some early enlistment details. Additional information on pre-World War I records available for researching enlisted army personnel, as well as those who served in the navy and Marine Corps, can be found in the article “An Overview of Records at the National Archives Relating to Military Service.”