CHICAGO — For a while, it seemed Joan Benoit Samuelson might do it again. The Freeport resident has set myriad running milestones in her decades of competitive running, and Benoit’s time Sunday in the Chicago Marathon could have been another special one.

Samuelson ran the course in 2 hours, 47 minutes and 50 seconds. That she won the 50-54 age group was almost a given — her time was nearly half an hour ahead of the second-place finisher in the division.

The time was two minutes off the qualifying standard for the 2012 U.S. Olympic trials.

Samuelson, who is 53, finished 43rd overall among women. She crossed the halfway mark in 1:21:09, well on pace to qualify for the Olympic trials. But her times dropped off in the later miles, perhaps due in part to the unusually warm weather. It was 67 degrees at race time.

“I went through 10 miles in 60 (minutes), so I knew I was going to be in trouble then,” Samuelson told Universal Sports after the race. “It wasn’t a smart race, but it was my race and that’s the way I had to do it today.

“I must say that at around 20 miles I saw the time and temperature sign and it said 80 degrees. At that point, I was hoping that I could run sub-three (hours). I put my goal of under 2:50 by the wayside and focused on getting in under three hours because I lost so much speed by going out as fast as I did.”

Benoit said she was running the Chicago Marathon, in part, to commemorate the 25th anniversary of her American record marathon time of 2:21:21, which stood until 2003.

She also said she was running to promote the activity “as a platform to really get our nation up and moving.”

“It’s so affordable and accessible,” she told The Associated Press. “Running is a sport for life. You don’t have to run marathons to be a runner. Why not at least get out and try?”

Sammy Wanjiru of Kenya won his second straight men’s race, finishing in 2:06:24, good for a 19-second win. Liliya Shobukhova repeated in the women’s race, crossing in 2:20:25. Wanjiru became the youngest runner to win four major marathons, with his other two titles coming in London and the Olympics.

The win all but assured Wanjiru of the World Marathon Majors series championship and the $500,000 that goes with it — something Shobukhova locked up after a personal-best 2:20:25. Both took $75,000 for finishing first and an additional $40,000 in performance bonuses.

“Today was a big day,” Wanjiru said. “It was for the leader points.”

Knee and back problems limited Wanjiru this year, and a stomach ailment a few weeks ago almost knocked him out of the Chicago Marathon. He missed a week’s training but decided to run, anyway.

Shobukhova grabbed the lead in the 21st mile after trailing by 24 seconds and ran away with her third major marathon championship and second this year to go with her win at London in April. She walked away from this event $615,000 richer, money she will use to build a hotel with her husband in her hometown. As for the race, she said, “I was controlling” it and never felt like it was getting away from her.

Astede Baysa of Ethiopia, the pacesetter for much of the morning, finished second at 2:23:40. Russia’s Maria Konovalova (2:23:50), American Desiree Davila (2:26:20) and Germany’s Irina Mikitenko (2:26:40) rounded out the top five.

There were 45,000 runners registered, and 38,132 made the start. Of those, 36,159 finished on a sunny day with temperatures in the low 80s.