In 1930, the state highway between Middletown and Mount Pleasant was finished. By 1931, the remainder became a state highway. When Delaware started numbering state highways by 1936, this road remained unnumbered.
What is now DE 71 originally existed as a county road by 1920, with the portion south of Townsend proposed as a state highway at this time. By 1924, the entire length of the present route was paved, with the portion from the Summit Bridge to Kirkwood proposed as a state highway and the portion from Kirkwood to Tybouts Corner improved to a state highway. A year later, the state highway had been completed south of Townsend and between Mount Pleasant and Kirkwood.