Rockfield was a hamlet that was annexed by the Village of Germantown in Washington County, Wisconsin, United States. A post office called Rockfield was established in 1876, and remained in operation until it was discontinued in 1997. The community was named from a nearby field containing marked rocks. The area is rich in Silurian limestone, and b…Rockfield was a hamlet that was annexed by the Village of Germantown in Washington County, Wisconsin, United States. A post office called Rockfield was established in 1876, and remained in operation until it was discontinued in 1997. The community was named from a nearby field containing marked rocks. The area is rich in Silurian limestone, and beginning in the 1870s quarries and lime kilns operated in the area.