CONCORD, N.H. — The Karner blue butterfly, once considered extinct in New Hampshire, has made a comeback.

The state Fish and Game Department says the number of butterflies marked in the wild surpassed the previous high number observed in 2010, which was more than 2,600. This year’s final count is still being worked on.

The department says good weather, coupled with help extending the butterfly’s unique habitat in Concord, have made a difference. A company called Praxair Surface Technology/TAFA created a 10- to 15-acre habitat to attract the brilliant blue butterflies, planting more than 600 blue lupine and nectar plants, the insect’s main source of food, in a matter of hours.

“The work that was completed by the staff of Praxair/TAFA would have taken a week or more for our limited staff to complete,” said John Kanter, coordinator of the Fish and Game Department’s Nongame and Endangered Wildlife Program.

The butterfly has been on the federal Endangered Species list since 1992. That year it also was named New Hampshire’s state butterfly. The state has been working to restore their unique, savannah-like habitat, as legislators realized the numbers were dwindling.

By 2000, biologists working to assess populations in the state found only one of the butterflies left in the wild. Fledgling efforts to monitor and preserve them led to a series of agreements among the state, city of Concord and New Hampshire Army National Guard, which provided a building that served as a greenhouse to grow butterfly eggs and wild lupine.

After a decade of carefully monitoring them and restoring their specialized habitat, even enlisting schoolchildren to help grow and plant lupines, the Karner’s population has rebounded. The summer’s count is expected to come the closest to reaching the federal recovery goal of 3,000 Karner blues in New Hampshire.

The butterfly itself was discovered in the 1940s in Karner, N.Y., by Russian author and lepidopterist Vladimir Nabokov. It was once seen in 13 states, but that’s gone down to about half because of a loss of habitat. Their range does not include Maine.