📜 Historic masonry bridge in Cabin John, Maryland, part of the Washington Aqueduct. 🔍 Designed by Alfred Landon Rives and built by the U.S. Army Corps of Engineers, it was the longest single-span masonry arch in the world when completed in 1864. # Why Go 🌉 Admire a significant civil engineering landmark, designated a National Historic Civil Engineering Landmark and listed in the National Register of Historic Places. 🚶 Walk or bike on the dedicated pathway, part of the MacArthur Boulevard Bike Trail. 💧 See an active aqueduct still supplying water and supporting vehicle traffic. 🏛️ Learn about its Civil War-era political controversies. # Why Avoid 🚦 One-lane traffic with signals can cause delays. # Tips 🅿️ Roadside parking is available along MacArthur Boulevard. ❄️ Road maintenance crews are reminded not to salt the roadway in winter months.