Big River Running Company and Fleet Feet Sports have each announced a new trail race to launch in fall 2015.

The inaugural Flint Ridge Trail Run from Big River Running will take place on Saturday, September 19, at Indian Camp Creek in St. Charles County. Distances include 10 miles and 4 miles. Registration is open at www.flintridge10.com.

The race will be the first run of the 2015 Big River Trail Series, a competition in which points are tallied for runners that participate in three of the four events at the Flint Ridge Trail Run (excluding the 4-mile race), the Skippo and the Castlewood Cup. Points will be calculated for runners that participate in each event.

Fleet Feet Sports plans to host Quivering Quads II, a fall version of its spring Quivering Quads race, on Saturday, October 31, in Cuivre River State Park in Troy, Mo. The new race will make use of the most enjoyable 13.1 kilometers (8.1 miles) of Quivering Quads’ 13.1-mile, half marathon course.

Quivering Quads II participants will skip the equestrian trail and the out-and-back finish that help make Quivering Quads a particularly challenging half marathon. To ensure the trails don’t become overcrowded, the Quivering Quads II field will be limited to 550 registrants. Registration is open at www.fleetfeetstlouis.com.