Christina Kouros is a national champion.

A 16-year-old junior at Cape Elizabeth High School, Kouros won the 5-kilometer women’s adaptive sit-ski competition Thursday at the U.S. cross country ski championships at Black Mountain in Rumford.

“Great performance by her,” said John Farra, head of the U.S. Paralympic Nordic program. “Really good stuff.”

Also at Black Mountain on Thursday, Dan Cnossen, a former Navy Seal who is a double amputee, won his first national title, the 10K men’s adaptive sit-ski race.

In morning racing, Tad Elliot of Durango, Colo., won the 15K men’s freestyle title and Jessie Diggins of Afton, Minn., won the 10K women’s freestyle title, her second of the week.

Both Elliot and Diggins are members of the U.S. Ski Team. The men’s field numbered 201 and the women’s field 161.

One day after taking second place in sprints around a relatively flat 800-meter course, Kouros showed off her double-poling abilities over more varied terrain.

“This was a World Cup-esque course with lots of climbing,” Farra said of the 2.5K loop that five sit-skiing women covered twice. “It was great to see (Kouros) have the strength to pull that off.”

The sit-skiers started at 30-second intervals, with Kouros bringing up the rear behind Wednesday’s sprint champion Sarah Edwards of Colorado and Alicia Dana, a competitive hand cyclist from Vermont in her first year racing on snow.

Through the first lap, Kouros remained behind Edwards and Dana. Not until the penultimate hill did Kouros make her move, passing both women on the climb.

“That’s my strength, is up the hills,” said Kouros, who raced for her high school team last winter and will continue to do so this season, if snow allows.

Kouros maintained her lead through the finish line, which she reached in 25 minutes, 1.7 seconds. Edwards was second in 25:40.3 and Dana third in 26:46.6.

“I look up to Sarah,” Kouros said. “I’ve been training with her for a while and I was just hoping to keep up with her. I didn’t really expect to place ahead of her.”

The warmer temperatures – in the upper 20s most of the afternoon – and softer, more forgiving snow aided the racers. Kouros said she needed fewer layers. Farra reported fewer crashes.

“Everybody had a great day,” he said.

Joining Cnossen on the men’s podium were runner-up Sean Halsted of Washington and Andy Soule of Texas.

In the morning freestyle races, Elliot covered a 15K course that included four trips up Black Mountain’s infamous “High School Hill” in 30:18.8. Runner-up Matt Liebsch of Minnesota finished within three seconds of Elliot with Bates College graduate Sylvan Ellefson of Colorado third, seven seconds behind the leader.

Diggins won her 10K title by more than a minute in 24:56.3. Daria Gaiazova, who moved to Canada from Russia at age 15, was second and Caitlin Gregg of Minnesota third.

Among skiers with Maine ties, Cape Elizabeth native Clare Egan placed 11th in the women’s 10K race, just over two minutes behind Diggins.

Lucy Garrec of Freeport and the University of Vermont was 15th in 27:15. Bethann Chamberlain of the Maine Winter Sports Center took 25th in 27:56.

Middlebury College teammates Emily Attwood (Cape Elizabeth) and Rachel Hall (Cumberland) placed 66th and 87th, respectively.

Colby teammates Molly Susla (Freeport) and Amy Lones (Cumberland) finished 113th and 142nd. Hilary McNamee of Fort Fairfield and the Maine Winter Sports Center was 130th.

For men with Maine ties, Sam Tarling of Cumberland and Dartmouth College did not start, nor does the reigning NCAA 10K freestyle champion plan to race in today’s 30K classical mass start.

“I’ve been a little under the weather,” Tarling said by phone Thursday night. “Hopefully I’ll race on Sunday (in the classical sprints).”

Nils Koons of Sidney placed 16th Thursday, less than a minute behind Elliot. Mike Lessard of Greene and the Maine Winter Sports Center placed 49th with MWSC teammates Welly Ramsey of New Sharon in 55th and Fred Bailey of Andover in 80th.

Other Maine men, and how they fared: Spencer Eusden (South Paris, Bowdoin) was 97th; Tom Rabon (Turner, Burke Mt.) 100th; Nick Michaud (Fort Kent, Bates) 114th; Derek Rowe (Farmington, MWSC) 147th; Tom Reagan (Freeport, University of New Hampshire) 156th; and Justin Fereshetian (Turner, UMaine-Presque Isle) 186th.