The Southern Trails Loop is a 2.1-mile hike in William O’Brien State Park. The trail passes through hardwood forests of red oak, white oak, aspen, and maple on gently rolling hills. There are also some open prairie areas. There is a fee to enter the park; a day use or annual permit can be purchased at the Park Office. Dogs are allowed on this trail when on a leash.

This hike can be started in two locations, from a parking lot off Ostrum Trail to the north or at the lot off Broadway Street to the south. This article will describe the hike starting from the lot off Broadway Street. This lot is located less than a mile west of the town of Marine on St. Croix just past the railroad tracks.

Start your hike by heading north on a mowed path. After about a tenth of a mile the trail splits, go to the right here to take the trail in a counter-clockwise direction. At the quarter mile mark, there is a wide, straight trail to the left; continue straight a head here through the forest. After the about two thirds of a mile the trail enters an open prairie area. Continue past some buildings that were once a private residence. There is a trail to the right here the leads to the northern parking lot.

Shortly after leaving the buildings, there is an unmaintained trail to the left. Stay of the main trail to the right; from here it about a mile back to the trailhead. The rest the hike is a mix of open areas and woods.

A map of all the hiking trails at William O’Brien State Park can be found here.