Most people in the valley today know the name Winnecook from the ranch, not the post office — but the two share the same story. Ralph Berry was born November 13, 1850, in Unity, Maine, and came west as a young man. In 1880 he traveled to Utah to bring back a band of sheep, while his brother, Samuel Berry, located a ranch along the Musselshell River and built two log cabins on the site. The Berry Brothers Ranch, as it was first known, grew into a substantial sheep operation, running as many as 40,000 head at its peak.

The Winnecook name itself traveled west with the Berrys. Near their hometown of Unity, Maine, sat a small, well-loved lake called Winnecook Lake, also known as Unity Pond — a name drawn from the Penobscot language meaning “pleasant water.” With the Musselshell running nearby, the family gave the same name to the post office they opened at the ranch on January 9, 1885, with Ralph Berry as its first postmaster. It was the first post office in the Musselshell Valley below Merino.

In 1887 Berry partnered with Frank Webster to form the Berry-Webster Sheep Company, registering the “W Lazy B” brand — for Webster and Berry — on the Winnecook Ranch. The partnership was dissolved in 1896, and the following year Webster took over as postmaster, with Theresa Stevens succeeding him in 1901. The post office continued to serve the ranch and surrounding valley into the new century.

Over the following three decades, the postmastership passed through several more hands — including members of the Wellington family, Blanche R. Clark, and finally Elwyn H. Dole — before the Winnecook post office was discontinued in the spring of 1933, a casualty of the Great Depression. The Winnecook Ranch itself remains today, on private land a short distance north of the highway between Shawmut and Harlowton — a lasting namesake for the valley's first post office below Merino.

Sources: Dodge, Dave, and Cleve Kimmel, “Out in the Boonies (Trip #14): Abandoned Historical Post Offices in Wheatland County,” rootsweb.com, 2008; and “Yesteryears and Pioneers,” Harlowton Woman's Club, 1972, including postmaster records cited therein from the National Archives, Washington, D.C. — viewable via Montana Memory Project.