The Virginia Department of Transportation found footage of US 29 (Lee Highway) from Key Bridge to Cherrydale filmed in 1949. VDOT recreated the same drive and combined that and the 1949 footage into one video and posted it on youtube:
The 1949 footage isn’t perfect, but still gives an idea of post-WWII Arlington County. Streetcars are visible and along with the billboards that faced Georgetown at the Virginia end of Key Bridge. It’s also noteworthy that there are two US 29 signs visible, but not US 211 which was officially multiplexed with US 29 until 1980 according to the Virginia Highways Project when it was officially truncated at Warrenton. I had previously heard 1984, but I suspect that the completion of Interstate 66 outside the Beltway hastened the demise of US 211 since it was no longer than only continuous route number from the Shenandoah Valley to Washington, D.C. This video suggests that the predecessor agency of VDOT and/or Arlington County was disinterested in the US 211 designation near Washington in that designation long before it was technically removed.
In the last frame, beyond the intersection of Kirkwood Road, is a trestle for the Washington & Old Dominion Railroad. That right-of-way would later be used for Interstate 66, completed in 1982 and the Custis Trail, BeltwayLand’s most challenging bicycle path. Starting that year, the intersection with Kirkwood Road was also the northern terminus of the George Washington Memorial Parkway according to Steve Anderson’s dcroads.net. Since 1959, that part of the GW Parkway has been a spur called Spout Run Parkway.
Highway markers from Shields Up!