The two people fell about 70 feet (21 meters) Saturday when part of the Arch Rock overlook at Point Reyes National Seashore gave way.
"Visitors using Bear Valley Trail to Arch Rock -- watch out! At the very end of the trail, the cliff is breaking away -- seen here in a photo taken Wednesday," the government organization said.
The NPS said
hazardous conditions had been reported to it on March 19.
John Dell'Osso from the Point Reyes National Seashore told CNN that it had posted warnings after being notified last Thursday that a crack had formed in the arch.
"We posted all kinds of notices up and down that particular trail, which is how probably how 99% of the people who would hike that far would (go), and all around our visitors' center in Trail Heads, just to warn people of the hazard that was out there," Dell'Osso said.
"We didn't know what could happen and what unfortunately did happen is on Saturday afternoon a large portion of that overlook actually collapsed down onto the beach and partly onto the ocean," he said. "The tragedy is that there were two people that were standing out there who fell with all of that rubble."
On Monday, the Marin County Sheriff's Office named the deceased as 58-year-old Nancy Blum, from California.
It said she had been hiking about 6:30 p.m. Saturday "when a structural collapse of the rock occurred."
After emergency personnel reached Blum and her hiking companion, she was flown to Bear Valley Ranger Station, where she was pronounced dead.
The National Park Service and the county coroner's office are investigating the cause of Blum's death.
"The cause of death will be pending the completion of toxicology studies," the sheriff's office said in a statement.
Bluffs along the California coast are known for being unstable, according to the park service. The Arch Rock trail that runs along that part of the coast has been closed until further notice.