MARC, the commuter train that operates in Maryland and which I take to and from work 4 days a week, has an article in their December 2007 newsletter (p. 6) about the dinosaur fossils that have been collected near their Muirkirk station in Prince George's County. The bones were found, as recently as 2006, on the grounds of a nearby brick manufacturing and clay mining operation.
According to the article: "The climate at Muirkirk was moist and humid, similar to Mississippi or Louisiana, with lush vegetation. Dinosaur bones from the Cretaceous Period (65-144 million years ago) have literally been excavated from a clay pit next to the train station."
Station under attack! Photomontage (by Frank Fulton) from the MARC newsletter.
There is so much creationist nonsense and intelligent design mumbo-jumbo being spewed out these days that it is a relief to come across instances of real science being presented to the public by a public agency that is not otherwise engaged in science. Kudos to the Maryland Transit Administration.
The article notes that the Maryland-National Capital Park and Planning Commission is planning to build a Dinosaur Park at the site. According to a budget document I found at the Commission's web page, the Dinosaur Park is scheduled for completion in June 2010, if, I suppose, funds continue to be available.
The article also mentions the finding of one particular dinosaur fossil: "In 1991, another amateur paleontologist, Arnold Norden, discovered of[sic] the femur (leg bone) of an Astrodon in the Muirkirk clay pit."
Arnold Norden, who goes by the name Butch among those who know him personally, happens to be the anonymous bioblitz team member pictured on this post from June 2006 with his face really close to the ground. At that time, he was looking for snails, not dinosaur bones.
A pamphlet titled Dinosaurs of the District of Columbia by Peter M. Kranz provides succinct historical information, especially suitable for young readers, about the dinosaur fossils that have been recovered around DC.