parts of the river along the Cumberland Plateau flow along Pennsylvanian-era siltstone, shale and sandstone. Along the river's Highland Rim portion, Mississippian-era limestone is more common. Karst features such as sinkholes and caves are not uncommon in this area. One of the state's largest caves, Cumberland Caverns, is located within the Collins watershed. The Barren Fork empties into the Collins east of McMinnville. Other tributaries include Big Creek and Savage Creek, which join the river at Savage Gulf, Hills Creek and Scott Creek, which empty into the Collins just north of the Warren-Grundy line, and Charles Creek, which empties into the river downstream from McMinnville. History During the late 18th century, the Old Kentucky Road, which roughly followed an old Indian path, crossed the Collins River at Shells Ford, near modern McMinnville. A string of other commonly used fords were located just above the mouth of the river, including Flat Shoals Ford, near modern Campaign. Reed's Ferry, later known as Black's Ferry, operated near the modern U.S. Highway 70S crossing throughout much of the 19th century. In the late 19th century, businessman Asa Faulkner constructed a wooden bridge across the mouth of the river as part of his Falls City development. Around 1900, Warren County built four bridges over the river: the Hennessee Bridge (approximately 8 miles above the river's mouth), the Lusk Bridge (near McMinnville), and Martin's Ferry Bridge and Harrison's Ferry Bridge, both located on the upper part of the river. A flood in late March 1902 destroyed Faulkner's bridge and two of the county's bridges– the Hennessee and the Lusk– along with bridges over Barren Fork and Charles Creek. The Tennessee Electric Power Company built the truss bridge which still spans the mouth of the river as part of its Great Falls Dam project in 1916, and rebuilt and raised the bridge in the mid-1920s. The current vehicle bridge, which runs adjacent to the truss bridge, was built by the Tennessee Department of Transportation in the 1980s. Recreation Most of the Collins River was designated a "scenic river" as part of the state's Scenic Rivers Program. The lower of the river were removed from this designation in 1983, however, and the scenic designation now applies only to the upper parts of the river at Savage Gulf. A scientific state natural area now protects the Savage Gulf area. This area is also part of South Cumberland State Park.