The following highways are numbered 623:
| Preceded by 622 | Lists of highways 623 | Succeeded by 624 |
State Route 235 is a primary state highway in the U.S. state of Virginia. The state highway runs 5.05 miles (8.13 km) between intersections with U.S. Route 1 in Fort Belvoir and Hybla Valley. SR 235 forms a southeast loop off of US 1 through the community of Mount Vernon in southeastern Fairfax County, connecting US 1 with Mount Vernon, the plantation home of George Washington, and the southern end of the George Washington Memorial Parkway.
Maryland Route 623 is a state highway in the U.S. state of Maryland. The state highway runs 7.26 miles (11.68 km) from MD 161 in Darlington north to State Route 2043 at the Pennsylvania state line in Flintville. The first section of MD 623 was constructed in the mid-1930s south from the state line. The state highway was extended south to Darlington in two segments in the 1950s.
King's Highway 109, or Highway 109, is a former provincial highway in Ontario. It was used on two separate, unrelated routes during the 1950s and 1960s:
Secondary Highway 500, commonly referred to as Highway 500, was a secondary highway in the Canadian province of Ontario which was first designated in 1956. Its route was renumbered in 1964, becoming:
Secondary Highway 514, commonly referred to as Highway 514, was a secondary highway in the Canadian province of Ontario. It was used on two separate routes from the 1950s to the 1990s:
