This is a map gateway into the database. Hovering provides a summary of the feature in the topmost layer underneath the mouse. Select or deselect layers in the control box at right. Clicking at any point (sometimes twice depending on browser) generates a popup with links to database pages to details on each of the three layers at the point you clicked.

Accumulating too many tooltips or control boxes behaving badly? Refresh the page.
Need access to Alaska, Hawaii, or Puerto Rico? Zoom out and pan the map.