"They're building a city," said Haverford Township's deputy police chief, John Viola, who serves as a liaison between the township and the tournament.
Ardmore Avenue - which bisects Merion's East Course - and Golf House Road, which borders the course's 14th and 15th holes, were overrun with trucks of all sizes this week, hauling items such as bundles of plywood and full-size office trailers.
Fences covered in green burlap have appeared along the course's borders, and towering bleachers now appear around many holes.
Palatial tents, meanwhile, have been built everywhere - on the course, at neighboring Haverford College, and on the front yards of several houses along Golf House Road.
The U.S. Golf Association was unable on Wednesday to provide information about the extent of the construction.
But Rick Ill, chairman of the U.S. Open for the club, said the infrastructure on and around the course has "exponentially grown up overnight."
"There are grandstands in spaces I didn't think they could fit anything," he said.
Neighbors have noticed the increased din of construction recently, including chiseling jackhammers, humming generators, and whizzing saws that echo for hours every day.
"There's noise at 5:30, 6 a.m.," said Suzanne Goodwin, a Golf House Road resident. "Trucks, workmen, going bang, bang, bang."
For some, like Goodwin and Chalmers Cornelius, who lives on Andover Road around the corner from Golf House Road, the construction has proved a nuisance.
Cornelius, who has lived there since 1971, said he was "slightly annoyed" with the hubbub, estimating that traffic has increased "200 to 300 percent" recently as tents were raised on neighbors' lawns.
The activity wasn't nearly as extensive in years past, Cornelius said. When Merion hosted the U.S. Open in 1971, his son sold lemonade to the golfers right on the course, he said.
"Now, you probably wouldn't get near the golfers," he said, noting the maze of tents and fences being erected.
Others, however, have accepted the construction and are looking forward to the tournament.
"The excitement keeps building," said Mary McBride, 65, another Golf House Road resident, whose house looks out over the course.
She's begun stocking up on food, beer, and wine, since their road will be closed during the tournament, and said police have explained how they will get their mail delivered and what security measures are being taken.
"They've really kind of provided for everything," she said.
Whatever the reaction to the construction, one thing is clear: with one spin around the course, it's impossible to miss the fact that the U.S. Open is less than two weeks away.
"If you'd be up there today," Viola said, "you'd see it's a beehive of activity."
Contact Chris Palmer, 609-217-8305, firstname.lastname@example.org, or follow on Twitter, @cs_palmer