"This will be a beautiful corridor for people to move through, live by and do business in," said Salt Lake City Mayor Ralph Becker.
It will be a "critical" link for the Parleys Trail, Becker said, connecting the Bonneville Shoreline Trail to the Jordan River Parkway.
Salt Lake City and South Salt Lake officials also believe the S Line will attract economic development.
South Salt Lake Mayor Cherie Wood said already various interests have expressed desires to build along the line in her city from 500 East to 200 West.
"Now it's more than just a concept," she said. "This corridor will reconnect our two communities."
Becker hailed the day as the result of a partnership with the federal Department of Transportation, which he praised for working with local governments and UTA.
UTA will begin testing the streetcar next week, but don't look for one of those cute, little cars that take San Francisco visitors halfway to the stars. Steve Meyer, UTA's chief capital development officer, said out of economic necessity the transit agency will employ modified TRAX cars at least for now on the S Line.
Officials unveiled a photograph of the streetcar Thursday. The vehicles themselves apparently were not ready for a debut appearance.
They will be trimmed with silver paint, rather than the TRAX red and blue.
The cars will seat 65 riders with an additional 35 standing. UTA estimates a daily ridership of about 3,000.
Eventually, the S Line will be composed of two tracks along the old railroad right of way that runs east and west at about 2250 South. For now, however, one track will be utilized by two streetcars. A siding at the 500 East stop will allow the streetcars operating in opposite directions to pass.
There will be seven stops, including those at Central Pointe and McClelland. The vehicles will travel 15 to 20 mph and will complete a one-way trip in 20 minutes, Meyer said. UTA has yet to determine the cost of a ticket.
Earlier this year, the Salt Lake City Council identified an extension route of the line that would continue east to Highland Drive and then north to 2100 South. It would continue north on the street that becomes 1100 East to 1700 South. No funding or timetable has been identified for construction of that extension.