According to historical writer and blogger Leon J. Pollom, the lowest section of Forbes Avenue was originally named Diamond Street.

[2][3] At approximately 6:45 AM EST on January 28, 2022, the Fern Hollow Bridge carrying Forbes Avenue over Fern Hollow Creek in Frick Park collapsed, injuring ten; the bridge was just west of the intersection with Briarcliff Road.

Six vehicles were left trapped in the rubble, including a Port Authority articulated bus.

The westernmost terminus of Forbes Avenue lies at Stanwix Street in the downtown part of the city.

From Oakland, Forbes Avenue continues eastward past 20th- and 21st- century Carnegie Mellon University and late 19th century Schenley Park, through the small stores of Squirrel Hill, and past Homewood Cemetery and Frick Park before it reaches its eastern terminus at the site of the January 2022 Fern Hollow Bridge collapse.