You'll find several sites tracing Lewis and Clark around Nebraska City. The Missouri River Basin Lewis and Clark Interpretive Trail and Visitor Center makes a good starting point, with indoor exhibits and nature trails featuring flora and fauna that the explorers encountered. Arbor Day sites are bountiful, too. For a primer—plus orchard-fresh apples in fall and a 50-foot-tall treehouse—visit Arbor Day Farm. Then, tour the estate of Arbor Day founder, J. Sterling Morton, at Arbor Lodge State Historical Park.