Just two riders boarded the first train Monday morning, but Metro expects ridership to reach about 27,000 daily.
The train officially opened to the public Saturday, when 44,000 people climbed aboard for free to celebrate its premiere. However the $1.50 one-way fare did kick in Monday. Seniors pay just 55 cents one-way.
The Expo Line connects Flower Street in Downtown L.A. to Jefferson Boulevard and La Cienega Boulevard. It will reach eventually reach further into Culver City by the summer and then into Santa Monica by 2016.
Construction on the $2.2 million project is funded by Measure R. Voters approved the county-wide 1/2 cent tax in 2008.
Councilman Jose Huizar was expected to greet passengers arriving at Union Station and those leaving at Flower Street and 7th Street Monday.