The southern end of Jack Slough Bridge as seen from a trail to the east. The water visible in this picture is not Jack Slough itself but a flooded area just south of it. Photo by queerbychoice. Jack Slough Bridge is a bridge across Jack Slough on Highway 70 at the north end of Marysville. It should not be confused with the railroad bridge that crosses Jack Slough about one thousand feet east of Highway 70.