[8] Faithful to his Beaux-Arts training, Flagg allowed space around the tall building for light to enter, which was unusual for the time.

[9] Though Flagg is best known for his large institutional designs, he was also interested in producing modest, attractive homes affordable to average Americans.

Flagg argued in favor of zoning laws which would regulate the height and setback of buildings, to allow light and air to reach the streets below them.

A small collection of Flagg's personal and professional papers is held in the Department of Drawings & Archives at Avery Architectural and Fine Arts Library at Columbia University.

The homes that Flagg designed are modest, low to the ground, with stone walls, and often with steep roofs, distinctive ridge dormers, and round-capped chimneys.

[8] In the Milwaukee, Wisconsin, area, over two dozen of these homes were built from 1924 to 1926, and they survive largely intact, now listed on the National Register of Historic Places.

[11] In 1912, Flagg and his wife were on their way to a party held by Stowe Phelps, a fellow architect, when their limousine struck and killed a boy (James McNamara) who had suddenly skated in front of the car.