The St. Charles Streetcar Line, officially Route 12 of the New Orleans Regional Transit Authority (RTA), is the oldest continuously operating streetcar line in the world. Passenger and freight service began on September 26, 1835 under the New Orleans and Carrollton Railroad, originally powered by steam locomotives — two engines, New Orleans and Carrollton, supplied by B. Hick and Sons of England — before transitioning to horse and mule power, experimental ammonia and Lamm fireless engines, and finally electrification on February 1, 1893. The line runs 6 miles (9.7 km) on a 5 ft 2.5 in (1,588 mm) gauge, mostly in the grassy "neutral ground" median of St. Charles Avenue and South Carrollton Avenue, with curbside running in the Central Business District.

The route links Canal Street, at the edge of the French Quarter and the Central Business District, with the Carrollton neighborhood at South Carrollton and South Claiborne avenues, passing through the Lower Garden District, the Garden District, Uptown and the Riverbend. It is the busiest route in the RTA system, used daily by both commuters and visitors. In 1973 it was listed on the National Register of Historic Places (reference 73000873), and on August 25, 2014 the National Park Service designated it a National Historic Landmark — one of only two moving streetcar landmarks in the United States, the other being the San Francisco cable car system.

Service was suspended after Hurricane Katrina in 2005 and restored in stages between 2007 and 2008. The line is operated from the Carrollton Station car barn at 8201 Willow Street, a steel-framed depot dating to 1893.

The classic shot is a green 900-series car framed by the canopy of live oaks along the upper St. Charles Avenue neutral ground in the Garden District and Uptown. The mansions between Jackson and Louisiana avenues — including the Columns Hotel at 3811 St. Charles and the so-called Wedding Cake House at 5809 St. Charles — make strong backgrounds. Lee Circle (Tivoli Circle) and the Riverbend, where the tracks curve from St. Charles onto South Carrollton Avenue, offer dynamic curve shots. The Carrollton Station car barn at 8201 Willow Street is the place to see cars stabled, but it is a working facility — photograph from public sidewalks and do not enter without permission.

The line's signature equipment is the 900 series: 35 olive-green streetcars built in 1923-24 by the Perley A. Thomas Car Works of High Point, North Carolina. Riders sit on reversible mahogany seats beneath exposed ceiling fans, with the windows cranked open because the historic cars have no air conditioning — the same cars New Orleanians and visitors have ridden for roughly a century. The wooden window sashes, brass fittings and clattering ride make a trip on the 900s a working museum piece rather than a re-creation.

To meet a 2017 accessibility consent decree, the RTA added seven 457 series cars — Perley Thomas-style replicas originally built with wheelchair lifts for the Riverfront Line — repainting them from red into the St. Charles green livery; accessible service began on December 1, 2020, while the historic 900 cars themselves were left unmodified. For railfans, the line offers a rare chance to ride genuine 1920s electric streetcars in regular revenue service, photograph them running through tunnels of live oaks, and see the 1893 Carrollton car barn where they are maintained.

The St. Charles line operates 24 hours a day, with cars roughly every nine minutes between 7 a.m. and 10 p.m. Most of the route runs in the landscaped neutral ground, so boarding is from low platforms or the median; in the Central Business District the cars run curbside along Carondelet and St. Charles streets. Fares are paid onboard with exact change or the Le Pass mobile app — drivers do not make change.

Expect a slow, frequently-stopping ride. The line is popular with tourists, and cars can be standing-room-only, especially midday and during festival season. The open windows mean you feel the heat and humidity, so the ride is most comfortable in the cooler months. A full end-to-end trip from Canal Street to South Carrollton and South Claiborne avenues takes roughly 45 minutes to an hour each way.