DUNDEE, Miss. (AP) — Wearing aqua-colored T-shirts and hydration backpacks, a group of teenagers on Saturday launched a 50-mile walk from northern Mississippi to Memphis, Tennessee, a tribute to slain civil rights leader Martin Luther King Jr. on the 50th anniversary of his assassination.

Escorted by police cars, support vans and a portable restroom, six middle school, high school and college students, along with two adult mentors, began their march in rural Dundee. Their journey along Highway 61 will take them past Mississippi Delta fields and farms, then the casinos of Tunica, before they me...