The Day Estate Historic District encompasses a subdivided estate at the corner of Commonwealth Avenue and Dartmouth Street in Newton, Massachusetts. The district is bounded by Commonwealth, Dartmouth, Chestnut, and Prince Streets, and includes six houses. It was originally owned by Henry Day, a banker, who in 1896 built the house at 321 Chestnut Street. They subdivided the block during a building boom in the 1920s, and the new houses were built between 1928 and 1930. Most of the new construction were high quality Tudor Revival structures designed by William J. Freethey. Day's estate house is now home to the All Newton Music School.