Maria Lydig Daly was born to a wealthy New York family of Dutch origins. Her father Philip Mesier Lydig, a merchant, was the last owner of the land that subsequently became the Bronx Park and now contains the New York Botanical Garden. In 1856, she married Charles P. Daly, who became a New York politician and judge. At age 37, she began keeping a diary. She was a prominent society hostess and pro-Union figure during the U.S. Civil War, and was active in the Democratic Party, the Women's Central Association for the Relief for the Army, and the NY Botanical Garden. Her diary, with its rich details of social life in the Civil War period and its aftermath, was later edited by Harold W. Hammond and published in 1962 as Diary of a Union Lady, 1861–1865.