Conversation so far:
Where did Murray Rothbard go to school?
Murray Rothbard attended Birch Wathen, a private school in New York City.
Did Murray Rothbard study anywhere else besides Birch Wathen?
Murray Rothbard attended Columbia University.
What did Murray Rothbard study at Columbia University?
Murray Rothbard received a Bachelor of Arts degree in mathematics in 1945 and eleven years later his PhD in economics in 1956.
Did Murray Rothbard do any research?
The delay in receiving his PhD was due in part to conflict with Murray Rothbard's advisor, Joseph Dorfman, and in part to Arthur Burns’s rejecting his doctoral dissertation.

Question: What did he do after his time in college?
Self-contained rewrite: What did Murray Rothbard do after his time in college?