Maryland is a fairly small state, but some very big dinosaurs have been discovered there, as listed below. (See an interactive map of dinosaurs and prehistoric animals in the United States.)
The official state dinosaur of Maryland, Astrodon was a 50-foot-long, 20-ton sauropod that may or may not have been the same creature as Pleurocoelus (below). In any event, the importance of Astrodon is more historical than paleontological; two of its teeth were dug up in Maryland in 1859, the first dinosaur ever to be discovered in this small state.
For all intents and purposes, Cetotherium can be considered a smaller, sleeker version of the modern gray whale, about one-third the length of its famous descendant. The odd thing about Maryland's Cetotherium specimen is that the fossils of this prehistoric whale have been most often found off the shores of Eurasia, not the Atlantic coast!
Maryland's official state fossil, Ecphora was a large, predatory sea snail of the Miocene epoch. If the phrase "predatory snail" strikes you as funny, don't laugh: Ecphora was equipped with a long, toothed "radula" that it used to bore into the shells of other snails and mollusks and suck out the tasty guts nestled inside.
Oddly enough, Pleurocoelus is the official state dinosaur of Texas, which no one would consider close to Maryland. As mentioned above, this sauropod may or may not have been the same animal as Maryland's official dinosaur, Astrodon, and in any case Texans have been lobbying to change their state dinosaur to something more home-grown.