Captain William Merrill, for whom the town is named, purchased the township in 1840, after which he and his son moved to the area sometime around 1844. Merrill was organized as a plantation for election purposes on September 6, 1858 from Township T6 R4, became formally organized as a plantation in 1876, and was incorporated as a town on March 4, 1911.
Merrill is served by Maine Route 212, just west of Smyrna, and Smyrna Mills straddles the ajoining boundaries of the two towns.