Dinosaur Park is the most productive dinosaur fossil quarry east of the Mississippi River, where fossils ranging from the bones and teeth of Maryland's state dinosaur Astrodon ohnstoni to the remains of early flowering plants help scientists reconstruct the region's ancient history. In 1858, African American iron miners working at this site discovered the first Maryland dinosaur fossils, and later John Bell Hatcher recovered many more fossils, including bones and teeth from six dinosaur species. Fossils are still found there today, and since 2009 the site has been preserved for scientific study and public educational programs as a cooperative project between the Maryland-National Capital Park and Planning Commission and Jackson-Shaw, developer of The Brick Yard, while also serving as an outdoor laboratory where the public can work alongside paleontologists. The fossils were deposited during the Cretaceous Period, from 145 to 66 million years ago, a time when the Jurassic landmasses began to break up into the continents and oceans of today, oceans expanded, climates became cooler and drier with more pronounced seasons, temperate forests spread across North America, and flowering plants became widespread alongside the first pollinating insects. About 110 million years ago, central Maryland was a flat coastal plain with winding rivers, and Dinosaur Park formed as part of an oxbow created when a sharp river bend became detached; during floods, drifting debris including dead plants and animals flowed into the oxbow, became trapped as waters receded, and was entombed in clay, creating the fossils found there.
