County Line is an unincorporated community located on the border of Marinette and Oconto counties, in the U.S. state of Wisconsin. The Marinette County portion of the community is located in the town of Grover, while the Oconto County portion is located in the town of Little River. County Line is located on County Trunk Highway W near U.S. …County Line is an unincorporated community located on the border of Marinette and Oconto counties, in the U.S. state of Wisconsin. The Marinette County portion of the community is located in the town of Grover, while the Oconto County portion is located in the town of Little River. County Line is located on County Trunk Highway W near U.S. Highway 41, 6.5 miles southwest of Peshtigo. East County Line Road and Old 41 Road intersect in County Line.