The Associates Building dominates the small Milton Village business district on the Neponset River. For an association of wealthy investors, Rotch and Tilden created a block in two sections that is visually united by the projecting brick diaper ornament at the third-floor level. The east half of the block has Queen Anne–style dormers and a gable roof, suggesting the traditional English medieval urban building with a dwelling over shops. The north half has a flat roof and heavy corbeled cornice in the style of a Renaissance palazzo. A terra-cotta sundial designed by Rotch features a hare, swallows, butterflies, a tortoise, and a snail. This block afforded the architects an important opportunity to demonstrate their ability to the many wealthy Bostonians having houses in Milton.

The ground floor originally contained the post office in the north end, followed by two stores and a bank. The local library occupied the south end of the block until 1902. An auditorium for concerts and lectures with offices, the stair hall, and a ticket office claimed the second floor. In 1929 alterations to the hall were made for the Masonic Association.