It began with a monument—a solitary cottonwood, remembered not for its grandeur but for the shade it gave weary travelers. It stood quietly for decades along the Platte River, a sentinel for westbound pioneers, a sacred meeting ground for the Pawnee, and a landmark that could be seen for 25 miles in any direction. That tree, known as the Lone Tree, may have fallen in a storm in 1865, but in 1988,…