YOSEMITE NATIONAL PARK, Calif. — Marilyn and Jack Whitcher have been regular visitors to the glacier-carved valley of Yosemite National Park since they were dating more than five decades ago. This trip was different.

“They changed all the names on us!” Mr. Whitcher, 75, said after stopping at a gift shop where the staff had just hours before cleared out all the T-shirts emblazoned with Yosemite National Park.

A bitter contract dispute has intruded into the Northern California wilderness, embroiling Yosemite, one of the country’s most beloved national parks, in the question of who, if anyone, should own the trademark to the park’s name and attractions. Delaware North, a company based in Buffalo, N.Y., has trademarked the name “Yosemite National Park” and other famous brands affiliated with the park, such as The Ahwahnee Hotel and the Wawona Hotel. The company is seeking $44 million for the next concessionaire to continue using them.

Shortly after midnight on Tuesday, when Delaware North’s contract to service the park expired, workers began riveting new names onto road signs and placing black tape over plaques that used the old names.