Marines who had served in the First World War gathered in New York City for the All-Marine Caucus at the Hotel Pennsylvania. Over four days the veterans' association took a new name, the Marine Corps League.

The caucus elected Major General John A. Lejeune, then Commandant of the Marine Corps, as the League's first National Commandant. The League counts 1923 as its founding year and Lejeune as its founder.

John A. Lejeune led the League as National Commandant from 1923 to 1929. He was followed in 1929 by Major General Wendell C. Neville, who had also succeeded him as Commandant of the Marine Corps.

W. Karl Lations then served as National Commandant from 1929 to 1931.

An Act of Congress approved on August 4, 1937 made the Marine Corps League a federally chartered corporation. President Franklin D. Roosevelt signed it.

The charter sets out the League's purposes. They include preserving the traditions and promoting the interests of the Marine Corps, bringing Marines together in fellowship, keeping the memory of Marines who gave their lives, and giving voluntary aid to Marines, former Marines, and their widows and orphans.

The charter is now part of Title 36 of the United States Code.

The Marine Corps League Auxiliary dates from 1937, the same year as the League's federal charter. It was founded to support the League and the Marines it serves, and it continues that work today.

The Military Order of the Devil Dogs, the League's fun and honor society, was founded in Boston in 1939. Its name recalls the nickname Marines earned at Belleau Wood in 1918.

The Order is known for its giving. Each year it gathers in a different part of the country and donates to a children's hospital there.

Marine veterans in Waterbury, Connecticut started a youth program in 1959 to pass on good citizenship and the values of honor, courage and commitment. The League's Brass City Detachment in Waterbury took a strong interest in the program and has supported it ever since.

At its 1965 national convention in Kansas City, Missouri, the Marine Corps League adopted the Young Marines as its national youth program. A Connecticut detachment member had raised the money to fly a whole Young Marine unit to the convention.

The program grew quickly as part of the League. In 1980 the Young Marines became an independent nonprofit organization.

June 2023 marked one hundred years since the League was organized in New York City. The League held its 100th national convention the following year, in Palm Springs, California.

A century on, the League still works to strengthen the fellowship of Marines and to serve Marines and FMF Navy personnel.

The Marine Corps League brought its national convention to Chicago in 1933. It was the League's 10th convention, and the first after a year in which none was held.

With the country at war, the League met in Chicago again in 1942 for its 19th national convention.

The Marine Corps League's Department of Illinois dates its founding to December 8, 1944. The Department brings the state's detachments together and helps start new ones wherever enough Marines live to form one.

The Department held its 82nd Department Convention in 2026.

The year after the Department of Illinois was founded, the League held its 22nd national convention in Springfield, the state capital.

The DuPage County Detachment, number 399, received its charter on April 30, 1977. It meets in Wheaton.

The Marine Corps League's National Headquarters chartered the McHenry County Detachment, number 1009, on October 27, 1998. The detachment meets in Woodstock.

The Lincoln Land Leathernecks Detachment was created in 2004. It meets in Greenville and gives to its local communities each year.

The League's 97th national convention met in Springfield in 2021. No convention had been held the year before, so it was the League's first national gathering since 2019.

Delegates in Springfield elected Johnny B. Baker of Georgia as National Commandant.

Members from across the state met in East Peoria for the 82nd Department of Illinois Convention. That year the Department counted 36 detachments in eight districts.