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Since 1988, the Interpretive Center, located within Ralph B. Clark Regional Park (off Rosecrans Avenue), has featured fossils for children, teens, and adults to enjoy. With displays devoted to Orange County’s rich geological past, the park’s nature center was originally established by the county to showcase fossils found during the development of the Emery Borrow Pit, land on which the regional park now sits on top. Since the late ‘80s, the Interpretive Center has expanded its educational programs and facility to become a nationally recognized home to one of the most significant fossil museums in Southern California.

When I was in elementary school, I remember visiting the regional park’s center and seeing really unique fossilized mammal skeletons in glass display cases, including a giant grand sloth and a ring-tailed cat. Recently, I reached out via email to interview OC Parks Resource Specialist Sarah Hoemke about what it’s like working at the nature center, how the park’s impressive fossil collection was originally discovered, and how the Interpretive Center has evolved over the years to include educational programs for everyone to enjoy.

“I am an OC Parks Resource Specialist and Certified Interpretive Guide assigned to Ralph B. Clark Regional Park,” said Hoemke via email. “I wear many hats here, creating and delivering public programs and school field trips, giving public tours, and coordinating volunteers inside and outside the Interpretive Center. The best part of my job is seeing the spark of awe in our visitors’ eyes when they learn about the animals that have lived here through all the changes Orange County has experienced over millions of years.”
According to Hoemke, the park’s nature center houses roughly three hundred fossils, ranging from marine fossils from up to 80 million years ago, to local land-roaming mammals from tens of thousands of years ago. She explained that since the start of Orange County’s Paleontology and Archaeology collection in the 1970s, approximately 1 million fossils have been collected.

“Since taking over management of the collection, OC Parks is working through a multi-decade backlog of stored materials that are awaiting or in the process of careful uncovering, identification and cataloging,” said Hoemke.

I learned from her that the park’s rich fossil beds were first discovered when the California Division of Highways excavated sand and gravel from the site during the construction of the I-5 and SR-91 Freeways from 1956 to 1973. She explained that at that time, the site the park now sits on was known as the Emery Borrow Pit. According to the regional park’s map and brochure, the County of Orange acquired the property in 1974 and Los Coyotes Regional Park opened in 1981. “The significance of the site led to public demand that it be preserved,” said Hoemke.

Over the years, the park’s Interpretive Center has gone through different renovations “to expand areas for storage and display,” according to Hoemke. She explained that in 2023, the Interpretive Center reopened after “undergoing a year-long renovation to repair roof panels, windows and structural beams.”

“The improvements will help preserve the integrity of the building and the unique fossil collections inside,” said Hoemke. “The repairs are part of our continued upkeep of the facility and commitment to improving and preserving the Interpretive Center for future generations to enjoy.”

The Nature Center museum is now home to the largest display of fossils from Orange County, including those recovered within Ralph B. Clark Regional Park, Coyote Hills, and other surrounding areas. I learned from first-hand experience that it also contains a fishbowl lab where visitors can view how fossils are prepared for research and display.

Hoemke said, “The center offers visitors of all ages an opportunity to enjoy and learn about Orange County’s pre-history and local paleontology…We have several popular exhibits displaying fossils from the late Cretaceous Epoch through the Pleistocene Epoch. One of the exhibits that stands out is ‘Joaquin,’ a 9-million-year-old, 26-foot-long baleen whale discovered during construction of the San Joaquin Hills transportation corridor in Laguna Niguel. Due to its size, the fossilized skeleton was separated into three sections so it could be supported and transported to the Interpretive Center in 1993 using a crane and a flatbed truck. Joaquin was excavated from a site containing fossil-rich sediments that accumulated between 4.5 and 9 million years ago. These fossils tell us about the ocean environment in Orange County during the Miocene Epoch.”

According to Hoemke, OC Parks runs monthly public programs aimed at both adults and children, with the goal of educating and inspiring individuals to learn about Orange County’s past, and teaching them to protect shared natural and cultural resources. She clarified that all programs at Ralph B. Clark Regional Park are offered free of charge.

OC Parks has been delivering programs that include tours of the fossil bed hillside for decades. On Saturday, February 15, 2025, park rangers are hosting an event called, “Explore! Fossils of the Ancient Sea Floor,” a guided tour of the Clark Regional hillside fossil bed, followed by a trip to the Interpretive Center. Advanced registration is required for both this and upcoming events, including:

“Preschool Paleontology: Art and Storytime” on Thursday, February 20 from 10 am to 11 am; “Jr. Ranger Time Scale Adventure at Clark Park” on Friday, February 21 from 3:30 pm to 5 pm; “Native Garden Restoration at Clark Park” on Saturday, February 22 from 8 am to 10 am; and “Explore! Fossils of the Ancient Sea Floor” on Saturday, March 15 from 8 am to 10 am. Additional information for each event can be found at http://www.ocparks.com/clarkpark.

Ralph B. Clark Regional Park is located at 8800 Rosecrans Avenue. Parking fees are $3 per vehicle entry Monday through Friday; $5 Saturday through Sunday. Fees are higher for some holidays and events.