BOSTON — For years, Kenyan athletes dominated the Boston Marathon. From Ibrahim Hussein’s win in 1991 to Wesley Korir’s in 2012, the Kenyan men won 19 times. The women had 10 victories since 2000.

But for the past four years, the Kenyan men hadn’t won at Boston. Ethiopian runners had won two of the past three women’s races.

On Monday, at the event’s 121st running, the Kenyans were emphatically back, with Edna Kiplagat putting down the hammer in the Newton Hills and winning the women’s race in 2?hours, 21:52 minutes and Geoffrey Kirui pulling away from Galen Rupp in the 24th mile to win his debut marathon in 2:09:37.

And the Americans were a presence, too. Rupp, the U.S. bronze medalist in the Olympic marathon last year, finished second in his first Boston Marathon. Six American men finished in the top 10. Jordan Hasay, Rupp’s Oregon Project teammate, finished third in the fastest debut time by an American woman (2:23:00) and Desiree Linden was fourth.

“I’m just thrilled to be a part of it,” said Rupp, who ran 2:09:58. “It’s so exciting to see Americans being competitive and running well here in Boston.”

Also running was Ben Beach of Bethesda, who completed the race for a record 50th time in a row. The 67-year-old finished with a time of 5:01:26. And Kathrine Switzer, wearing the same bib number — 261 — that she wore when she entered the all-male race 50 years ago, using only her initials, K.V.

Earlier, city officials announced plans for memorials to mark the sites where two bombs exploded during the 2013 race.

Also in the field was Boston Police Commissioner William Evans, who ran for the 18th time in 2013 but has skipped the races since the bombings so he could be available in case of another emergency. Evans, who completed his 52nd marathon overall, said he wanted to show that Boston is back to normal.

“If I can come back,” he said, “everyone can.”

In the wheelchair race, the Swiss dominated. Marcel Hug edged 10-time winner Ernst van Dyk at the finish line to win his third straight Boston Marathon men’s title in 1:18:04, breaking the 2012 course record. And Manuela Schar won the women’s title with a course record of 1:28:17. Clarksville resident Tatyana McFadden (Atholton), who won the race each of the previous four years, finished fourth.

Kiplagat, at age 38, won in her first trip to Boston. She won the London and New York City marathons in 2010.

“It was really great for me,” she said. “I was feeling good.”

Kenyan Rose Chelimo finished second in 2:22:51 and Hasay was right behind her in 2:23:00. Linden, who led the race from Mile 5 to 14 and was hoping to win after a close runner-up finish in 2011, finished in 2:25:06.

It was a warm day, with temperatures in the 70s, for the 30,000 runners who set off from Hopkinton in different waves Monday morning.

Rupp, who had only run two marathons before Monday (the Olympic trials and the Olympic marathon), enjoyed himself.

“I had a really good time out there,” said Rupp, who ran at the Manchester Road Race last November and is coached by 1982 Boston Marathon winner Alberto Salazar. “It exceeded any expectations that I had.

“Take nothing away from this guy [Kirui] here. He ran a heck of a race. I just didn’t have it over those last 3-4 miles. I felt pretty good coming through the hills, tried to push it a little bit. He put in a couple good moves. We got to the top of Heartbreak Hill and eventually I just couldn’t stay up with him.”

Kirui pulled away and finished strong.

“I was not aware I was going to win but according to my training, I knew also that I would challenge,” he said.

He didn’t know Rupp’s name and referred to him as “my friend from the USA.”

“After my colleagues from Kenya dropped out, I remained with this man from the USA,” Kirui said.

U.S. Olympian Abdi Abdirahman finished sixth in 2:12:45, beating out 2014 Boston winner Meb Keflezighi (13th in 2:17:00) as the top master. Shadrack Biwott (fourth), Augustus Maiyo (seventh), Luke Puskedra (ninth) and Jared Ward (10th) were the other Americans in the top 10.

Abdirahman, 40, led the race for a while.

“I was hoping to finish top three but that wasn’t possible,” Abdirahman said. “We got to 32K and my quads starting cramping, I don’t know why, I just couldn’t move. There was a point I thought I was going to stop, at 40K. I just walked in. I was happy with my sixth place.”

On the women’s side, Kiplagat started to hammer the pace in the hills and broke away from Hasay and Chelimo. Neither could stay with her.

“After halfway, I was feeling pretty good,” Hasay said. “I’m going to go with any move. Then when she did go, she just went so hard. I thought, ‘I don’t think I can go with this.’ I’ve never run a marathon. It was pretty far out still. I don’t really want to risk this. I just need to go my own pace. Maybe I’ll catch her, maybe I won’t.”

She didn’t, but was still happy.

lriley@courant.com

twitter.com/lrileysports

Associated Press reporter Jimmy Golen contributed to this article.