National Geographic Channel takes a break from world travel for a home-grown adventure borrowed from Huckleberry Finn. "Mississippi River Quest" follows a team of modern-day explorers as they tackle all 2,300 miles, which means, of course, an early stop in the Twin Cities. "Mississippi River Quest" is a three-part special on National Geographic that follows a filmmaker, a scientist and a professional fisherman as they try to ride the length of the Mississippi River in a variety of vessels. / The first hour, "Headwaters to Minneapolis" (at 7 p.m.) finds the three embarking in kayaks. That's followed by "Minneapolis to Memphis" (at 8 p.m.) and "Memphis to the Gulf" (at 9 p.m.). (Source: National Geographic Channel)