The Robert Street corridor from downtown St. Paul south to Rosemount is entering a new phase of study, following a $1.18 million federal grant last month. It's an alternatives analysis, to start within 6 months and finish between mid-2012 and the start of 2013. Streetcar/light rail and bus rapid transit options have been mentioned most often up until now, but no specific type of service has been determined yet.
According to the book Twin Cities by Trolley by John W. Diers and Aaron Isaacs, horsedrawn streetcars started serving Robert Street in 1887. Electric streetcars ran from 1891 until 1952. Two Twin City Rapid Transit streetcar services, "So. St. Paul" and "S. Robert", shared track from downtown across the river to Concord Street (officially Cesar Chavez today) and State Street. Rather than going straight south along Robert, the streetcars of the S. Robert service ascended the bluff along State Street, rejoined Robert Street a few blocks later, and ended at Annapolis Street. The service up the hill between Concord and Annapolis only lasted until 1938.
The So. St. Paul service was more heavily trafficked than S. Robert and continued along Concord Street. It's not entirely clear when the name came along, since the tracks initially only went as far as Witham Street, just east of today's U.S. 52 (Lafayette Freeway). In 1905, the service was extended about 5 miles through the city of South St. Paul to Linden Street in Inver Grove Heights.
In 1913–1914, the St. Paul Sothern Electric Railway built 17.5 miles of track from Inver Grove to Hastings. They had intended to reach Red Wing and Rochester, but never made it that far. The line opened in late 1914, but didn't have through service to St. Paul until an agreement was finally struck with TCRT almost a year later. The railroad carried on until 1928. TCRT took over a small stretch of track to Faulkner Ave in Inver Grove Heights, but abandoned that in 1933, cutting back to the earlier Linden Street terminus.
With this history in mind, I'm not entirely sure whether a future "Robert Street Corridor" would actually continue along Robert Street or if it would go along Concord instead. Of course, both services would probably be useful, so I wouldn't want to be restricted to an either-or scenario. There are definitely a lot of stuff along Robert Street today, though a good chunk of it is a post-1950 "Anywhere, USA" business corridor. Looks can be deceiving, and I'm a bit concerned that the number of residents within walking distance could be pretty low.