Many of these fossils are on display in the museum’s Siebel Dinosaur Complex, where visitors can view Montana’s T. rex, one of the few mounted Tyrannosaurus rex skeletons in the United States, the bones of "Big Al", a nearly complete Allosaurus that lived during the Jurassic Period, numerous dinosaur eggs and babies, and more.

In addition to dinosaurs, the museum contains a large collection of prehistoric mammals that once roamed the state, including mammoths, rhinos, and bone-crushing dogs. These fossils and more are on exhibit in the Siebel's Cenozoic Corridor.

Visitors to the museum can see fossil preparators at work in the Bowman Dinosaur Viewing Lab where they carefully remove the rock that has encased fossils for millions of years so that the specimens can be studied. Every day, new discoveries are being made at MOR.

Each year, the paleontology field crew sets off into the rocky outcrops of the Treasure State in order to collect more information about what the world was like millions of years ago and how it and the creatures that have inhabited it have changed through time.

This data-rich exhibit engages visitors in the science of paleontology: how we know what we think we know about dinosaurs. At every turn, you will encounter the latest research on life in the Mesozoic Era, abundantly evident in Montana, as well as the processes of research. Visitors are challenged to formulate their own hypotheses about dinosaur growth, development, behavior, and interactions with their environments. As new discoveries and scientific breakthroughs are made, visitors will see changes in the exhibit.

The Siebel Dinosaur Complex houses the Dinosaurs Under The Big Sky exhibit, one of the largest and most up-to-date dinosaur exhibits in the world. In 2003, Thomas and Stacey Siebel donated $2 million to help triple the museum's dinosaur exhibit space. They were impressed by the museum's user-friendly approach to explaining complex concepts, especially for children. The Siebel Dinosaur Complex was built based on the children's book Dinosaurs Under the Big Sky authored by renowned paleontologist and MOR's former Curator of Paleontology Jack Horner, who also contributed to the exhibit's design.

The new exhibit, Cretaceous Crossroads, opened in early July 2025.

Did you know that some of the oldest rocks in North America are found in Montana? Travel through 4.6 billion years of Earth’s dynamic prehistory as you begin your journey through time in the Siebel Dinosaur Complex. Walk through the reconstruction of a 2.7 billion-year-old fissure, explore how mountains have risen and seas have spread, and encounter some of the many organisms that evolved in the northern Rocky Mountains region.

Visit the Bowman Dinosaur Viewing Lab and see the process of fossil preparation. Watch MOR volunteer preparators remove rock from around the bones of dinosaurs and other ancient creatures and carefully piece the fossils back together. Preparators are happy to answer your questions and explain how they ready these specimens for study.

The lab is active seven days a week between the hours of 10 a.m. to 4 p.m.

Hall of Giants

Begin your journey through the Age of Dinosaurs in the Hall of Giants. Enter the Jurassic Period and encounter "Big Al", one of the most complete Allosaurus ever discovered. This Jurassic carnivore’s skeleton records evidence of a hard life, including injuries and infections.

As you enter the Cretaceous Period, you will meet Deinonychus. The discovery of this relative of Velociraptor helped cement the link between ancient dinosaurs and modern birds.

As the tides change, dip under the surface of the seaway that covered much of North America during the Cretaceous, and keep an eye out for carnivorous marine reptiles.

Then, peek inside the lair of Oryctodromeus, the first dinosaur discovered inside a burrow.

Mesozoic Overlook

How do fossils get to a museum? Explore the process of paleontology, from the small fragments of bone that first reveal that a dinosaur skeleton is nearby, through the collection, preparation, curation, and study of the creatures found in the Siebel Dinosaur Complex. This vantage point provides an overview of the skeleton of "Big Al" and the other inhabitants of the Hall of Giants. 

A staircase located adjacent to the Bowman Dinosaur Viewing Lab will lead you up to the Overlook. Alternate access to the Overlook can be achieved via elevator by inquiring at the Front Desk.

On Earth, it is generally true that where there is water, there is life. This was certainly the case with the Western Interior Sea during the Late Cretaceous. This large seaway, which bisected North America, was not only teeming with marine life; it also cultivated a rich habitat for plants and animals along its shores. As mosasaurs and other aquatic reptiles hunted beneath the waves, tyrannosaurs ascended to the top of the food chain on land, where they remained until the end of the Cretaceous, when the age of the dinosaurs drew to a close.

For the first time in over ten years, Museum of the Rockies unveiled this new primary paleontology exhibition on July 2, 2025. Cretaceous Crossroads explores this time of transition, with a focus on three geologic formations in Montana (Two Medicine, Judith River, and Bearpaw) that span the period from 72 to 82 million years ago. The exhibit is comprised of real fossil material, 3D prints, casting, reproductions, murals, new paleo-art, AV interactives, an augmented reality piece, microscope stations, discovery drawers, and more.

Visitors will see a mounted Maiasaura (Montana’s State Fossil) tending to its nest, a 30-foot-long

Daspletosaurus horneri (large meat-eating dinosaur, cousin to T. rex, dinosaur eggs and clutches, Troodon (small raptor-like dinosaurs), a 23-foot-long Mosasaurus, and many other specimens, some of which are only known from Montana. This includes never-before-seen specimens that are not just new to Museum of the Rockies; they are new to science!

Enter the world of the Hell Creek Formation and meet some of the last non-avian dinosaurs to roam Montana, including Triceratops and Tyrannosaurus rex!

Tyrant Kings 

Come face to face with a world-class T. rex fossil collection including the largest and smallest skulls ever discovered! Explore what this famous dinosaur ate and how it lived. Tyrannosaurus rex, meaning “tyrant lizard king,” roamed the earth 65 million years ago. Now among only a handful of museums in the world to display a fossilized T. rex skeleton, this exhibit presents one of the most spectacular specimens ever unearthed called Montana’s T. rex. Discovered near the Fort Peck Dam and one of the most complete T. rex skeletons ever found, Montana’s T. rex stands 12 feet tall and approximately 40 feet from nose to tail. It would have weighed almost seven tons as it walked the eastern regions of the state. The Tyrant Kings, featuring Montana’s T. rex presents the science and research of Tyrannosaurus rex in a very, very big way.

Triceratops

Explore one of the largest Triceratops collections, which reveals how this famous three-horned giant grew and evolved. From baby to behemoth, learn how MOR’s Triceratops discoveries have shed light on dinosaur biology, growth, and diversity. See Triceratops develop from baby to adult in a series of skulls, ending with one of the largest dinosaur skulls ever discovered! Skeletons of an adult and a juvenile Triceratops pace warily near Montana’s T. rex, and a tyrannosaur-bitten hip bone shows what happened when these animals got too close!

Sixty-six million years ago, a mass extinction event ended the reign of the non-avian dinosaurs and brought the Mesozoic Era to an end. This marked the beginning of the Cenozoic Era, a time when mammals, a group of animals that had lived in the shadows of the dinosaurs for over 100 million years, came to dominate the Earth.

The Cenozoic Corridor highlights the fossils of mammals and other creatures that roamed Montana after the Age of Reptiles, including ancient horses, bison, mammoth, rhinoceros, and a bone-crushing dog.