Which investment firm did Warren Buffett work for after graduating from Columbia?

After graduating from Columbia, Warren Buffett worked for Graham-Newman Corp.

Buffett studied under Benjamin Graham at Columbia Business School and earned a master's degree in economics in 1951. He first worked at his father's firm, Buffett-Falk & Co., from 1951 to 1954. In 1954, he joined Graham-Newman Corp. as a securities analyst, beginning a particularly influential phase of his career.

Graham-Newman was the investment firm associated with Benjamin Graham and Jerome Newman. There Buffett worked alongside investors including Walter Schloss and applied Graham's value-investing principles: analyze a company's fundamentals, seek a margin of safety, and look for securities priced below their underlying worth.

The firm closed in 1956 when Graham retired from active investing. Buffett then returned to Omaha and established his own investment partnerships. Merrill Lynch and Goldman Sachs are plausible Wall Street distractors, while Buffett-Falk & Co. was his father's firm and therefore belongs to an earlier part of his career—not the post-Columbia job asked about here.