The caption reads:  Take a good look at these Tampa streetcars.  You won't see them after today.  They will be replaced tomorrow with buses, ending more than half a century of service on Tampa streets.  The cars go into the barn tonight to be sold to Central and South American countries to spend their last days "south of the border."

The USF Special Collections On-line library has an excellent article on the history of streetcars in Tampa and St. Pete.  This article shows the retirement date of the streetcars as 1949, but the Streetcar Society says 1946.  It could be that from August 1946 to May 1949, the cars were gradually taken out of operation.

See the article at:  http://www.lib.usf.edu/ldsu/digitalcollections/T06/journal/v19n1_97/v19n1_97_37.pdf  It also contains many interesting pictures.  Well worth your visit.

An excerpt from that article, on the topic of the retirement of the streetcars...

...although some officials, including Mayor Bruce Blackburn, fought against the proposal.  By January 1948, most of the cars had been taken out of service, and on May 7,1949, the last streetcar in the Tampa Bay area made its final run with windows draped in black crepe and a sign reading “Not Dead Just Retired.”