The surface road layout in Washington, D.C., consists primarily of numbered streets along the north–south axis and lettered streets (followed by streets named in alphabetical order) along the east–west axis. Avenues named for each of the 50 U.S. states crisscross this grid diagonally, and where the avenues intersect, traffic circles often occur. Many circles are named for American Civil War generals and admirals, while several neighborhoods take their names from nearby circles. There are approximately 36 roundabouts currently in the District.