The grueling 70.3-mile (113-kilometer) race will include a 1.2-mile swim in Mercer Lake, a 56-mile bike ride, and a 13.1-mile run along a rural course. It will start and end in West Windsor.
"It's really exciting," said Colleen Fossett, a founding member of the Mullica Hill Women's Triathlon Club. She plans to make it her first half-Ironman. "There will be a big interest in it."
The race will be directed by Glassboro-based CGI Racing Inc., which manages three other triathlons in the state, including the largest - the New Jersey State Triathlon at Mercer County Park.
"It brings triathlon to a whole new level in this area," said Michele Redrow, president and CEO of CGI.
Redrow said CGI approached Ironman several years ago and suggested an event in Mercer County. It will give the region's numerous tri-clubs a chance to compete against top professional athletes.
"It's been a long time coming," Redrow said. "We couldn't be any more excited than we are right now."
Meckfessel said the Princeton area was selected because of its proximity to New York and Philadelphia. Mercer County also has experience hosting big events and will host the National Special Olympics next summer.
"It is a very exciting time for us in Mercer County," said County Executive Brian Hughes. "We are pleased to have them."
The event is expected to pump between $3 million and $6 million into the local economy over the course of the race week, according to the Princeton Regional Chamber of Commerce and Princeton Regional Convention and Visitors Bureau.
"Little Mercer County. We're like a little engine going up the hill," said Hughes.
Meckfessel said the Mercer County event would be annual. World Triathlon, which owns and operates Ironman, previously staged a half-Ironman in the Poconos, but that was halted in 2012.
Two years ago, World Triathlon canceled its New York City Ironman because of logistical problems and pushback over a $1,200 entry fee.
The entry fee for the Mercer County event will be $275.
"It's going to be a great race," said Nick Pomponio, 62, of Washington Township, who has participated in several Ironman events and teaches a triathlon workshop at Rowan University. "I'm looking forward to signing up."
The location, timing, and mostly flat Mercer County course make this "within a lot more people's reach. I expect that race to be a big draw," he said.
Fossett, 44, of Mullica Hill, said the race would likely attract other athletes like her who have longed to try their first Ironman. She predicted that as many as 80 members of her club might participate.
"It's a huge deal for a sanctioned Ironman event to come to New Jersey," she said. "It's a perfect opportunity."
General registration for Ironman 70.3 Princeton opens at noon Dec. 16 at www.ironman.com/princeton