The late afternoon sun was beating down on a crowd of athletes outside Princeton University’s DeNunzio Pool and Weaver Stadium on Monday, but nobody seemed to mind. Having just completed Day One of the Special Olympics USA Games, these competitors were pumped.

“It’s fun. I love it,” said William Quinn of the Pennsylvania delegation, the second largest group of athletes after New Jersey. Having competed in the pentathlon 400 and long jump, the 32-year-old was feeling good. So was teammate Tamika Newkirk, a competitor in shot put, long jump, and the 100-meter run. “When I run, I stay focused and everything is a whole lot easier for me,” said Ms. Newkirk, who is 42. “I have wonderful coaches. They love me so much. It’s a good thing.”

New Jersey’s hosting of this national event follows four years of careful planning by Special Olympics New Jersey, which is headquartered in Lawrence Township. The games showcase the athletic abilities of people with intellectual disabilities and celebrate the Special Olympics movement, which promotes acceptance and inclusion through sports. A group of 52 people ran down Nassau Street Saturday to open the games as part of the Law Enforcement Torch Run.

Athletes are being hosted at venues including Princeton and Rider universities, the College of New Jersey (TCNJ), the Lawrenceville School, Hun School, Peddie School, and Mercer County Park. The games began officially with an opening ceremony at Newark’s Prudential Center Sunday, and will culminate Friday at Trenton’s Sun National Bank Center.

More than 800 athletes were flown in and will be flown out from Trenton-Mercer Airport, free of charge, as part of the Cessna Citation Airlift. Physicians from all over the country took part in a “Healthy Athletes” program at TCNJ early this week, offering their services free of charge. A “Special Olympics Town” at TCNJ has a Jersey shore boardwalk theme with rides, games, and vendors. The list of special events is extensive.

New Jersey athletes taking part in the games represent every county in the state, competing in 16 sports including aquatics, track and field, baseball, basketball, bocce, bowling, cycling, flag football, golf, gymnastics, powerlifting, soccer, softball, tennis, triathlon, and volleyball. Eight of the teams are competing on Unified Sports teams, which pair athletes with intellectual disabilities and those without, on the same team.

“These kinds of events just make people happy,” said Martha Costa, an employee of the Princeton University Store, while riding back into town from the University venues on one of the First Transit buses employed for the occasion. “We’ve seen a lot of people come in from all over — South Carolina, Texas, Tennessee. One young man who does shot put came in with his Dad and was very proud of the fact that he’s from Arkansas. It was really nice to see.”

Bus driver Barbara Baldwin, making the runs between Palmer Square and the University venues, said the buses had been filled nearly all day. “It’s so exciting to see the kids’ faces when they get on,” she said. “And then when they come out of the events, you see them pumping their fists. It’s just so inspiring.”