PORTLAND – The rail executive who helped transform Amtrak’s Downeaster from a dream more than a decade ago into a reality late last year is stepping down from his post this summer.

Michael Murray worked on the Boston-to-Portland project for more than 12 years and served as executive director of the Northern New England Passenger Rail Authority since its inception in 1995.

The rail authority announced Monday that Murray decided against extending his contract when it expires on July 29.

The chairman of the rail authority and the leader of a rail advocacy group gave credit to Murray for seeing the project through despite some rough periods including seemingly interminable delays.

The delays would have been even longer without Murray’s patience and perseverance, said Wayne Davis of TrainRiders Northeast.

“Mike is clearly going to be missed. He’s someone who has set the stage for this project to now progress further into Maine and to be a true success story,” added Jon Carter, the rail authority’s chairman.

Under Murray’s leadership, the rail authority oversaw the rehabilitation of 78 miles of track owned by Guilford Rail Systems between Portland and Plaistow, N.H., and oversaw all contracts needed for the rail service.

Murray’s decision comes as the service continues to show solid numbers. Ridership and revenues have exceeded projections each month since the first train rolled out of Portland on Dec. 15.

As of April 1, 85,249 passengers had ridden the Downeaster with revenues of $1.33 million. Official numbers are not available for April, but those numbers are expected to exceed expectations as well.

“Mike has put his heart and soul into it, and the project wouldn’t be a success without Mike at the helm,” Carter said.

Davis said Murray wanted to get the trains rolling and then move on. Nonetheless, he said the timing was a surprise.

This is a critical time for the rail authority, as it considers further expansion of service to other parts of Maine, he said.

Murray was not in the office on Monday and could not be reached immediately for comment. His home phone number is unlisted.

In a statement, he said he was honored to have been allowed to serve the people of Maine in creating the service. “This achievement is truly spectacular and one of which we can all be proud,” he said.

The Downeaster went into operation Dec. 15 with four daily trips in each direction between Portland and Boston.

Stops include Saco and Wells in Maine; Dover, Durham and Exeter in New Hampshire; and Haverhill in Massachusetts. A seasonal stop in Old Orchard Beach is expected to begin in July.