During the early 1900’s, the federal Government built a series of post offices throughout Canada. The Whitby Town Council petitioned the government for a new post office in May of 1903. The construction was approved and started in 1909 and in September 1910, it opened to the public.

The new post office was built of red and grey sandstone from Indiantown, New Brunswick. Gray and Son of Oshawa was the successful contractor who built the post office. The building boasted modern conveniences like electricity and hot water, and contained 3 floors. The ground floor housed the town's post office and the receiving room of the customs department. The second floor contained the customs office and the office of Inland Revenue.

A prominent feature of the post office was its clock tower. The clock was built in England and installed by Phillip Taylor, a Whitby Jeweler. Many of the townspeople set their watches according to the time on the clock tower.

At the time, there was no mail delivery, so residents would go daily to the post office to collect their mail from the series of 657 post boxes and 41 drawers available.

There was no official opening for the new post office. The keys were simply turned over to the postmaster, John D. Howden (1841-1927) on September 23, 1910 and Alex Whitelaw (1840-1929), the first caretaker, moved into his residence on the third floor. His duties included winding the clock every eight days.

The new post office would stand at the corner of Brock and Dundas streets for 50 years, before it was demolished in 1959.