David H. Koch Hall of Fossils — Deep Time

The Smithsonian National Museum of Natural History building on the National Mall opened to the public on March 17, 1910. From its earliest days, fossil displays were among the museum's most prominent attractions. The original paleontology exhibition was known as the "Hall of Extinct Monsters" and remained under the stewardship of curator Charles W. Gilmore from 1910 until 1945. The hall featured mounted dinosaur skeletons and other vertebrate fossils acquired through Smithsonian-led expeditions across the American West. The Diplodocus longus specimen (USNM 10865), collected by Gilmore and Norman H. Boss at Dinosaur National Monument, Utah, in 1923, was first mounted and placed on display in 1931 and measured approximately 87 to 90 feet in length.

Subsequent renovations occurred hall by hall during the mid-to-late 20th century, with the most recent major update completed in the early 1980s. By the 2010s, the five interconnected fossil halls—totaling over 65,000 square feet of mechanical, electrical, and structural infrastructure—had become outdated both scientifically and physically. In 2012, the Smithsonian announced the complete renovation project, and in April 2014, the existing halls were closed to the public. The five-year renovation proceeded in three phases: deinstallation of over 2,000 specimens (beginning April 2014, lasting 18 months), demolition and structural renovation (approximately 2 years), and installation of the new exhibition (18 months). More than 10,000 individual bones and other fragile specimens were removed, photographed, conserved, and in many cases 3-D scanned and re-posed before reinstallation.

The total cost of the renovation reached approximately $110 million. David H. Koch, executive vice president of Koch Industries and a longtime member of the NMNH board, provided a lead gift of $35 million—the largest single donation in the museum's history at the time. The Smithsonian Board of Regents approved the naming of the exhibition space in recognition of Koch's gift in April 2012. Approximately $70 million in federal funds covered critical infrastructure upgrades, including replacement of mechanical systems, air handling, electrical systems, windows, and lighting across all five halls. Additional private contributions supplemented the remaining costs.

The renovation was the largest and most complex in the museum's more than 100-year history. It transformed 31,000 square feet of exhibition space (equivalent to approximately six basketball courts) into a unified, narrative-driven exhibition.

Deep Time is structured as a journey backward through time. Most visitors enter from the museum's Rotunda and begin in the most recent geological period, encountering early human ancestors and ice-age megafauna, then travel progressively deeper into the past through 10 geologic time periods, ending at the formation of the Earth 4.6 billion years ago. The exhibition sections, in visitor sequence, include: the Warner Age of Humans Bridge and Gallery (10,000 years ago to the present), the Recent Ice Ages (Quaternary, 2.6 million years ago to the present), Mammals Take Center Stage (Paleogene/Neogene, 66–2.6 million years ago), Dinosaurs in a Flowering World (Cretaceous, 145–66 million years ago), Giant Dinosaurs Roam the World (Jurassic, 201–145 million years ago), From Mass Extinction to Amazing Variety (Triassic, 252–201 million years ago), Familiar Food Webs Emerge (Permian, 299–252 million years ago), Strange Forests of an Ice Age (Carboniferous, 359–299 million years ago), Life Evolves in the Ocean (Ediacaran–Devonian, 635–359 million years ago), Life Moves Ashore (Ordovician–Devonian), and The Long Beginning (Hadean–Proterozoic, 4.5 billion–635 million years ago).

More than three dozen murals by paleoartists Julius Csotonyi and Andrey Atuchin, along with sculptures by Alexandra Lefort and scale-model murals by Dwayne Harty, help visitors visualize ancient ecosystems. Thirteen videos and eight touchscreen interactives feature museum scientists and external experts. Dozens of touchable objects, including fossils up to 159 million years old, allow tactile engagement. Nine miniature dioramas depict the changing world through time. Some original murals by paleoartist Jay Matternes from the previous fossil hall have been reproduced or incorporated into the new exhibition.

The Nation's T. rex: The centerpiece of the exhibition is a nearly complete Tyrannosaurus rex skeleton (MOR 555), discovered in 1988 by Montana rancher Kathy Wankel on federal land near the Fort Peck Reservoir in eastern Montana. The specimen was excavated from 1989 to 1990 by a team from the Museum of the Rockies led by Jack Horner. It is one of the largest and most complete T. rex specimens ever found, with 80–85 percent of the skeleton recovered, and it was the first T. rex discovered with a complete forelimb. Owned by the U.S. Army Corps of Engineers, the specimen was loaned to the Smithsonian for 50 years beginning in 2014. In the exhibition, the T. rex is posed preparing to decapitate a fallen Triceratops.

Diplodocus longus (USNM 10865): Collected from Dinosaur National Monument, Utah, in 1923, this specimen stretches nearly 90 feet in length and was first mounted in 1931. It is one of the longest-displayed dinosaur specimens in NMNH history.

Allosaurus fragilis: Discovered in 1883, this specimen from Colorado is one of the most studied Allosaurus specimens in the world. In the exhibition, it is posed protecting a nest of eggs. In 2024, the Smithsonian announced that this skeleton had been designated as the neotype specimen for Allosaurus fragilis, making it the official name-bearing specimen for the species.

Stegosaurus stenops: A fully articulated skeleton displayed as it was found in the ground, located near the FossiLab area.

Megaloceros giganteus (Giant Deer): A fossil from Ireland, on display at the museum since 1872, making it the museum's oldest mounted fossil skeleton. It received a new pose for the Deep Time exhibition.

Other notable specimens include a Brontothere (Megacerops coloradensis) first mounted in 1920 (the oldest unchanged skeletal mount in the exhibition), Eoraptor lunensis (a cast of one of the earliest known dinosaurs), the phytosaur Smilosuchus gregorii, a Rhamphorhynchus pterosaur, American mastodon, woolly mammoth, Smilodon, Helicoprion whorl-toothed shark, a 308-million-year-old Lepidodendron lycopsid tree, and Ediacaran organisms from Canada dating to 565 million years ago.

The exhibition incorporates multiple layers of educational engagement. The Warner Age of Humans Bridge and Gallery, an elevated platform near the exhibition entrance, allows visitors to survey the entire sweep of deep time while considering how humans have become an unprecedented force of global change. A four-screen theater space in this section addresses modern climate change, and an interactive touchscreen invites visitors to consider individual and collective responses. This section was developed with input from an Anthropocene Advisory Council co-chaired by Scott Wing (NMNH curator of fossil plants), Jane Lubchenco, and Thomas Lovejoy.

The Coralyn W. Whitney Fossil Basecamp is a hands-on interactive area at the end of the exhibition where visitors can explore key concepts such as evolution, fossilization, and fossil dating, facilitated by museum staff. The FossiLab is a glass-enclosed, functional fossil-preparation space staffed by museum preparators and volunteers, where visitors can observe real specimen preparation in progress.

A dedicated audio-description app (available for iOS and Android) provides accessibility features, offering visual descriptions of the hall integrated with exhibit content.

The exhibition was developed by a core team of NMNH scientists and staff. Kirk Johnson, the Sant Director of NMNH (appointed 2012), a paleobotanist specializing in fossil plants and the K–Pg extinction, oversaw the project. Matthew Carrano, Curator of Dinosauria since 2003, served as lead curator. Anna "Kay" Behrensmeyer, Curator of Fossil Vertebrates and an authority on taphonomy and terrestrial paleoecology, was the lead scientist for the Deep Time Initiative. Scott L. Wing, Curator of Fossil Plants and an expert on the Paleocene-Eocene Thermal Maximum, contributed the climate-change narrative. Siobhan Starrs served as exhibition project manager and creative lead. Amy Bolton managed education and outreach integration.

A distinguishing feature of Deep Time compared to earlier fossil halls is its explicit integration of climate-change science. The exhibition draws parallels between past warming events—particularly the Paleocene-Eocene Thermal Maximum (PETM) of approximately 56 million years ago—and modern anthropogenic climate change. Key fossils such as Ectocion jaws from Wyoming (showing body-size reduction during the PETM) and damaged fossil leaves (showing increased insect herbivory) serve as tangible evidence of past biotic responses to warming. The exhibition presents two possible paths for Earth's long-term climate future, framing the choices as dependent on collective human action. This messaging was carefully developed with input from climate scientists and science-communication experts on the Anthropocene Advisory Council.

The exhibition draws upon the resources of the NMNH Department of Paleobiology, which curates over 40 million fossil specimens from around the world—one of the largest fossil collections on Earth. The department's staff includes experts in vertebrate paleontology, invertebrate paleontology, paleobotany, micropaleontology, and taphonomy. The museum's scientists publish hundreds of research papers annually (812 papers and 309 new species described in 2018 alone). The collection supports researchers from institutions worldwide.

The National Museum of Natural History is one of the most visited museums in the world, welcoming over 5 million visitors annually (down from a peak of approximately 7–8 million in earlier years). Admission is free. Deep Time has become the museum's flagship exhibition, serving as a gateway to scientific literacy for millions of visitors each year. Its design philosophy—emphasizing the interconnectedness of Earth systems, life, and human activity across billions of years—represents a paradigm shift from traditional fossil exhibitions that focused primarily on taxonomy and specimen display. By framing fossil evidence within the context of ongoing environmental change, Deep Time positions paleontology as directly relevant to contemporary challenges, particularly climate change and biodiversity loss.