|From:||King Street (NO114234)|
|To:||Tay Street (NO120234)|
|Length:||0.3 miles (0.5 km)|
|Met:||A9, A90, A85, A920|
|Route outline (key)|
The A921 is listed in the 1922 Road Lists as Perth (South Street from King Street to Tay Street).
The road crossed the town centre, as shown in the sketch map to the right, linking the A9/A90 junction on the now-unclassified King Street with the A85/A920 junction at the Victoria Bridge (now replaced by Queens Bridge).
Owing to the short length of the road it is not known exactly how long it lasted. Although the road is given Class I status at least until the 1970s the A921 number was reused elsewhere in the 1940s, giving the original incarnation a terminus ante quem. Certainly, the entire length of South Street, including the former A921, is now unclassified and one-way eastbound.