Fenn was established around 1910 as a planned townsite on the Canadian Northern Railway's Stettler Subdivision at milepost 64.3. Fenn was surveyed on a rise west of the tracks with ambitions for development, including a lot sale promoted with fanfare. However, its proximity to nearby settlements like Stettler and Big Valley prevented significant growth, limiting it to a local railway station, grain elevators, and a stock yard rather than a full town. A general store built around 1912 housed the post office, which opened in 1917, alongside a small residence and service station, while railway facilities included a freight and passenger shelter erected in 1916 and section crew bunkhouses until their removal in 1937.

The origin of Fenn's name remains uncertain, with possible sources including Fen County in England—due to similar marshy terrain—a young boy who assisted railway workers by hauling water, or an unnamed railway official. Despite its modest scale, Fenn persisted as a grain delivery point and supported railway operations, with the business track repurposed in 1990 for gravel loading from a nearby pit, a function that continues today under the Alberta Prairie Railway for material storage and transport. Today, few structures remain, including the former general store (now a private residence) and the relocated passenger shelter, marking Fenn as one of Alberta's smallest mapped communities with no formal population recorded.
The Post office opened on April 1, 1917. The first postmaster was O.L. Edstrom, who held the position until 1920.