This car is painted to honor Illinois Terminal Railroad System (ITS), which once ran an extensive interurban passenger service in southern Illinois.
Most of its service was run by classic interurban style electric cars. However, buoyed by what turned out to be artificially high ridership during World War II, ITS ordered eight double-end PCC streetcars for its shortest route–a suburban service running six miles from St. Louis, Missouri across the Mississippi River to Granite City, Illinois. Those eight PCCs had bodies identical to No. 1015 (except that the Illinois Terminal cars had no rear doors).

No. 1015 at Castro & Market. Georg Lester photo.

Like their Red Arrow cousins in Philadelphia, the Illinois Terminal PCCs were equipped for multiple unit operation and ran at times in two-car trains. However, despite the modern PCCs, the company saw patronage fall rapidly on the Granite City line as more commuters could afford — and chose — automobiles. The route was abandoned in 1958 and the PCCs were put up for sale. But their lack of rear doors and the high asking price kept buyers at bay.
All but two of the eight Illinois Terminal PCCs were cut up in 1964, but the survivors, Nos. 450 and 451, returned to service in Cleveland from 1975 to 1979, leased from the museums that preserved them to run on the Shaker Heights line during a severe car shortage.. But in their brief nine years of service, the big Illinois Terminal PCCs, like their longer-lived Red Arrow cousins, proved their capability in suburban service.
One wonders what might have been if Muni had made the commitment to upgrade the famed interurban 40-line to San Mateo with fast new streetcars like No. 1015, instead of abandoning the line in January 1949. None of Muni’s ten new double-end PCCs was even tried on the 40-line in the brief period between the cars’ arrival in San Francisco and the line’s abandonment, although the long-standing competition from the parallel Southern Pacific commuter trains (now Caltrain) and automobiles had badly undercut ridership, just as for ITS’ Granite City line.
Instead, No. 1015 ran on Muni’s J, K, L, M, and N lines until 1982, when it was retired and stored for a time, when it was restored to serve the new F-line starting in 1995.  After almost 25 years of daily service, it was restored again by Brookville Equipment Company in 2020.