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"Established in 1867 by its first resident, Juan Guitterez, the town was known for a time as “El Valle del Guitterez” because Mr. Guitterez grazed his cattle in the valley. Just to the west of the Guitterez ranch lived a fairly well known homesteader named James Stoner. Because of a rock formation on Mr. Stoner’s place, the region gradually became known as Stoner’s Wall. When the settlement grew large enough to need its own post office in 1878 the name became Stonewall."
"James Stoner: One of the early settlers in Stonewall, Stoner was actually the Postmaster. In those days the great geological feature that exists in Stonewall was called Stoner's Wall. The settlement became known as Stonewall after he died." Source: http://www.sangres.com/history/characters.htm
"The first Postmaster in Stonewall was named James Stoner and the Dakota Wall here was originally known as Stoner's Wall. When Stoner died the townsite became known as "Stonewall" and carries that name to this day." Source: http://www.sangres.com/colorado/lasanimas/stonewall.htm