He arrived in 1777 at the age of 23, and served as a military engineer in the Continental Army with Major General Lafayette. Despite his aristocratic origins, L’Enfant closely identified with the United States and changed his his first name from Pierre to Peter. L’Enfant served on General George Washington’s staff at Valley Forge.
In 1779 L’Enfant was wounded at the Siege of Savannah. He recovered but became a prisoner of war when the Americans surrendered Charleston, South Carolina, He was exchanged in November 1780 and served on General Washington’s staff for the remainder of the American Revolution. L’Enfant was promoted by brevet to Major in the Corps of Engineers on May 2, 1783, in recognition of his service to the cause of American liberty. He was discharged when the Continental Army was disbanded in December 1783.
L’Enfant also designed furniture and houses for the wealthy, as well as coins and medals, including the Purple Heart.
Enfant arrived in Georgetown on March 9, 1791, and began his work. Washington arrived later on March 28, to meet with L’Enfant and the Commissioners for several days.[26]
L’Enfant’s “Plan of the city intended for the permanent seat of the government of the United States…”\ specified locations for two buildings, the “Congress House” (the United States Capitol) and the “President’s House” (known after its 1815–1817 rebuilding and re-painting of its stone walls, as the “White House” or “Executive Mansion”).[31]
The “Congress House” would be built on “Jenkins Hill” (later to be known as “Capitol Hill”), which L’Enfant described as a “pedestal awaiting a monument”.[31][35] The “President’s House” would be located at a northwest diagonal from the “Congress House” along the future Pennsylvania Avenue.[22][31] The “President’s House” would be situated on a ridge parallel to the Potomac River, north of a riverfront marsh and a canal (known as “Tiber Canal” or the “Washington City Canal” during the 1800s).
L’Enfant envisioned the “President’s House” to have public gardens and monumental architecture. Reflecting his grandiose visions, he specified that the “President’s House” would be five times the size of the building that was actually constructed, even then becoming the largest residence then constructed in America.
The plan specified that most streets would be laid out in a grid. To form the grid, some streets (later named for letters of the alphabet) would travel in an east–west direction, while others (named for numbers) would travel in a north–south direction. Diagonal broader avenues, later named after the states of the Union, crossed the north–south-east/west grid. The diagonal avenues intersected with the north–south and east–west streets at circles and rectangular plazas that would later honor notable Americans and provide open space
L’Enfant laid out a 400 feet (122 m)-wide garden-lined “grand avenue”, which he expected to travel for about 1 mile (1.6 km) along an east–west axis in the center of an area that would later become the National Mall.[38][40] He also laid out a narrower avenue (Pennsylvania Avenue) which would connect the “Congress House” with the “President’s House”.[30][38] In time, Pennsylvania Avenue developed into the capital city’s present “grand avenue”.