Tap anywhere on the map to drop a pin, or search an address above — the pin's unit, its land and a box to name and save it appear straight underneath. Unit boundaries come from each state's own GIS layer, or the Census county lines where a state's units are its counties. Zoomed out, the whole country is drawn from one simplified map; zoom in and each state's full-detail lines take over. Near a unit line, confirm against the official boundary description.