LEWISTON — Over 66,000 Mainers have signed up for health insurance with Maine Community Health Options, an increase of 65 percent for the state’s only health insurance co-op.

Of those people, 57,600 got insurance through the federal marketplace established by the Affordable Care Act, also known as “Obamacare.” That means for the second year in a row, MCHO will insure the majority of Mainers on the marketplace.

“(The overall numbers) are right in line with what we had been working towards and what we were projecting, so it’s great to see coming into focus this way,” said CEO Kevin Lewis.

Co-ops are health insurance companies run by members for members. They were created through the 2010 Affordable Care Act to increase competition among health insurers and to provide consumers with greater choice in the marketplace.

There are 23 co-ops throughout the country. Rating company A.M. Best has said that, as of last fall, Lewiston-based MCHO is the only one making money.

As of Feb. 18, nearly 75,000 Mainers had signed up for insurance through the marketplace, according to the Centers for Medicare and Medicaid Services. About 57,600 of those Mainers chose one of MCHO’s insurance plans, according to preliminary numbers released by the co-op Tuesday. However, MCHO’s figures include only people who have paid their first bill.

With several days left for consumers to pay for March 1 coverage, Lewis expects that MCHO will ultimately be responsible for about 80 percent of the marketplace.

Last year, MCHO had about 83 percent of the marketplace. At that time only two insurance companies shared the marketplace — MCHO and Anthem Blue Cross and Blue Shield. This year, a third insurer, Harvard Pilgrim Health Care, has joined the marketplace.

More Mainers are signing up for insurance under the ACA. According to the latest Gallup pol l, 11.6 percent of Mainers were uninsured in 2014, down from 16.1 percent in 2013.

MCHO also started selling insurance in New Hampshire this year. So far 5,200 people there signed up for a MCHO plan. Lewis called that a “strong start” considering MCHO got a late start there and is one of five companies selling insurance through the marketplace in that state.

“I think we’ll be able to demonstrate to people in the Granite State the tremendous value that we offer,” he said.

Anthem spokesman Rory Sheehan said he was not able to release enrollment figures Tuesday because Anthem’s numbers would only be estimates. However, he said, the company is “encouraged by the significant interest we’ve seen in our plans.”

“We continue to see growth in the individual market and are pleased that our market share continues to increase from last year,” he said. “While nearly 75,000 people in Maine have signed up for plans on the exchange there are still many who do not have health insurance. We will continue to work to get the word out to people across the state about the benefits of quality and affordable health insurance and the availability of financial assistance.”

Harvard Pilgrim did not respond to requests for enrollment information.