He was from early life an investigator of American paleontology and natural history, devoting himself to the study of the shells of the Tertiary and Cretaceous formations, and to existing species of mollusks.

In 1831 he began the issue of a work on "American Marine Conchology", and the year following published the first number of his "Fossil Shells of the Tertiary Formation", which was never completed.

He was paleontologist of the New York Geological Survey from 1838 until 1841, and wrote the annual reports in that department.

[3] He defended the theory of periodical refrigeration, and suggested that the Mississippi depression was the consequence of the upheaval of the Appalachians and the later elevation of the area of the Rocky Mountains.

[3] The American Philosophical Society elected Conrad to Membership in 1865 for his contributions to science.