Halsey is a town in Marathon County, Wisconsin, United States. It is part of the Wausau, Wisconsin Metropolitan Statistical Area. The population was 651 at the 2010 census. The town is named for Pierson Halsey, a partner in the Milwaukee law firm of Rietbrock, Halsey and Johnson, which founded Athens, Wisconsin. It was set off from the town of Hamburg i…Halsey is a town in Marathon County, Wisconsin, United States. It is part of the Wausau, Wisconsin Metropolitan Statistical Area. The population was 651 at the 2010 census. The town is named for Pierson Halsey, a partner in the Milwaukee law firm of Rietbrock, Halsey and Johnson, which founded Athens, Wisconsin. It was set off from the town of Hamburg in 1883.