With ridership on the Blue Line light rail passing the 100 million mark, Metro Transit decided to celebrate Thursday.

Mascots “A” and “B” boarded a northbound train at the 46th Street Station and rode to Government Center Plaza to draw attention to the milestone and a contest to mark it.

Through Feb. 19, customers can post old and new photos highlighting trips taken on the light-rail line to Metro Transit’s social media accounts, including Facebook, Instagram and Twitter. Two randomly selected winners will get a $100 Go-To Card.

Formerly known as the Hiawatha Line when it opened in 2004, the Blue Line runs between downtown Minneapolis and the Mall of America in Bloomington.

More than 50 percent of train riders have become transit users since rail service began, Metro Transit said.

Last year alone, more than 9.5 million rides were provided on the line, which was built for $715 million.

Tim Harlow