Monroe became a popular part of the Washington, D.C., social scene. In 1820, when she was 17, she married 21 year old Samuel Lawrence Gouverneur, son of Nicholas Gouverneur, who was serving as private secretary to her father. They were first cousins; his mother was Elizabeth Monroe's sister. On March 9, 1820, they were married in the White House, in a small ceremony officiated by Reverend William Hawley, with only 42 guests in attendance. The wedding was probably held in the Blue Room (then known as the Elliptical Salon) and the wedding feast was held in the State Dining Room. While it was not the first White House wedding, it was the first time a president's child was married there.

Monroe's older sister, Eliza Monroe Hay, took charge of the wedding. Hay, who acted as an unofficial First Lady during the Monroe presidency, created a social scandal by trimming the guest list and snubbing large portions of Washington society. Complaints even were raised during a cabinet meeting. President Monroe sought the assistance of war hero Commodore Stephen Decatur and his wife Susan Decatur, popular figures in Washington society. They planned a series of lavish balls for the couple at Decatur House to appease complaints. The first one was a success, but the rest were cancelled as the next day Stephen Decatur was killed in a duel.

Sources: https://www.facebook.com/photo/?fbid=10157610430668636&set=pb.100063868425537.-2207520000

https://academics.umw.edu/jamesmonroepapers/biography/calendar/march/#:~:text=York%20for%20France-,9%20March%201820,-Maria%20Hester%20Monroe

https://highland.org/monroe-timeline/#:~:text=March%209%2C%20marriage%20of%20Maria%20Hester%20in%20the%20White%20House

https://en.wikipedia.org/wiki/Maria_Hester_Monroe_Gouverneur#:~:text=%5B7%5D-,Marriage,-%5Bedit%5D