Northern Frederick County is home to three historic covered bridges. All three bridges are listed on the National Park Service’s National Register of Historic Places. The Utica Mills, Loy’s Station, and Roddy Road covered bridges all cross streams in northern Frederick County, within twelve miles of one another. Besides their beauty, the bridges are also structurally interesting, as all three have different truss systems (which is what keeps a bridge standing). Motorcoach driving directions.