Entwistle was founded by James Entwistle, an employee of the Grand Trunk Pacific Railway (GTP). Entwistle knew that construction of the railway would be halted on the east banks of the Pembina River for a few years as a bridge was built over the river. A boomtown would most certainly spring up. Seizing the opportunity, Entwistle staked a claim on a section of land very close to the Pembina River and the surveyed line for the GTP in 1907. In 1908, as the railway construction camps drew closer to the Pembina River, Entwistle built a general store on his land, and left it in the care of his wife and children. The railway soon arrived, construction on the railway bridge started, and the boomtown formed around Entwistle's store.
The Post Office opened on June 1, 1908.