Few things are as American as racing, whether by foot, by automobile or by horse. Boat racing is pretty darn American too, so go cheer on competitors at the Riversport Challenge, a dual 500-meter kayak race and 5k running race as part of the SandRidge Energy Stars & Stripes River Festival. The whistle blows at 8 a.m., and events run through 10 p.m. in the Boathouse District, 725 S. Lincoln Blvd. Admission is free, while challenge registration is $35 for adults and $15 for children 12 and under. Call 552-4040 or visit boathousedistrict.org.