It will easily surpass the $40 million in economic impact and 15,000 hotel-room nights generated in 2002 by the X Games at the former First Union Center, which drew 235,000 spectators over 10 days.
Preliminary estimates from the U.S. Golf Association, the governing body that conducts the U.S. Open, project a total impact for the five-county Philadelphia area of $100 million to $120 million. Philadelphia and Delaware County, by virtue of their proximity to Merion - the golf club is in Ardmore - are expected to reap the greatest benefit, followed by Chester County.
About 190,000 spectators, volunteers, and staff are expected to attend, the USGA says. Spokesman Dan Hubbard said economic-impact numbers were a range based on how previous host cities did with the event.
The San Francisco Bay Area, for example, which includes Oakland and San Jose and is considered a larger tourist destination than the Philadelphia region, generated 112,000 hotel-room nights and $130 million to $150 million in total economic impact from last year's U.S. Open.
"It was an enormous coup," Anne LeClair, president and CEO of the San Mateo County/Silicon Valley Convention and Visitors Bureau, said of last year's U.S. Open at the San Francisco Olympic Club.
San Mateo County, just south of San Francisco, reaped $3.5 million in economic impact from the event, with thousands of hotel rooms booked, she said.
Said the USGA's Hubbard: "By all the indications we've seen, this one [Merion] will be extremely well-attended."
Total hotel-room nights during the U.S. Open are projected at 60,000 to 110,000 at suburban hotels and the 44 in Center City. The USGA itself booked 7,500 of those for staff, event sponsors, and golfers.
"It's definitely a worldwide event," said Lou Prevost, part-owner of the 171-room Radnor Hotel and the 40-room Wayne Hotel, noting that he started taking group bookings from companies in Germany, Ireland, Scandinavia, and Asia, primarily Japan, about a year ago. Many booked for the entire week, he said.
"The Europeans were not fazed at all by the rates," Prevost said, and several made dinner reservations at both hotels. (The special-event rate at the Radnor includes an "all-American pig roast" and the opportunity to watch the third round of the Open on a big-screen TV in the hotel's formal gardens June 15.)
Ann Armstrong, director of marketing for the 364-room Four Seasons at One Logan Square, said Friday that the hotel was anticipating a sellout for the week.
"We absolutely are getting a bump - a significant bump," she said, noting that about 60 percent of those bookings are U.S. Open-related.
Tore Fiore, executive director of the Brandywine Conference and Visitors Bureau, said Delaware County hotels typically had an average monthly occupancy rate of 68 or 69 percent.
"We are expecting at our 35 hotels and bed-and-breakfasts in Delaware County [with 3,500 rooms available] to be at a minimum 90 percent occupancy rate," Fiore said. "For the most part, the feedback we are getting is they're full to busting.
"You're seeing an overseas clientele coming in at a seven-night minimum stay," he said. "A lot of these visitors are either going to tag in three days in the front end or the back end for tourism and shopping."
It will be Christmas in June for Hamanassett, a bed-and-breakfast in Chester Heights, off Baltimore Pike.
In January, a company in York rented out the entire place for its best clients for the U.S. Open and secured about 15 daily passes to the event for them. Hamanassett will run shuttle buses to Merion three times a day.
Glenn Mon has owned the 11-room bed-and-breakfast with wife Ashley since 2001. The couple met at the Los Angeles Open in 1988.
"We made the USGA aware of our property and [had] it included in its listing of lodging," Mon said.
Ashley Mon has hired three extra housekeepers for the week to flip the beds daily and "make sure everything is perfect." The Mons are charging their usual rates, $200 to $279 per night per room.
Meanwhile, at the Radnor Hotel, the closest to the U.S. Open and located near the Route 100 Norristown High Speed Line that goes directly to Merion - a van will even drive hotel guests to the station hourly - Prevost said he was charging a higher rate than normal, $399 per room per night. The rate at his Wayne Hotel is close to that, he said.
All of these visitors will mean plenty of bodies on the move - which is why King Limo Inc. of King of Prussia - one of the region's largest limousine services - is reserving much of its fleet just for U.S. Open week, manager Andy Chorba said.
"They flat out tell you, 'We need transportation to the U.S. Open,' " Chorba said, describing the flurry of calls coming in. "They know it's going to be a crazy week, so everyone has their transportation lined up for it."
They're lining up their parties, too.
Carlino's Specialty Foods, an Italian market in Ardmore about a mile from Merion, says it's up 20 percent in bookings that week for catering services - golf tailgates, barbecues, and in-home private parties.
"People are coming in from all over the country. They want to entertain friends coming in," said third-generation owner Nick Carlino, 24.
The market, which includes a full-service deli and bakery, is adding an outdoor patio eating area that will be ready by Friday, in time for the Open.
"We wanted to do it anyway," Carlino said, "but the Open was a nice excuse."
Contact Suzette Parmley at 215-854-2855, email@example.com, or on Twitter @SuzParmley.