What was the name of the agency formed by Don, Roger, Bert, and Lane?

Don Draper, Roger Sterling, Bert Cooper, and Lane Pryce formed Sterling Cooper Draper Pryce. The agency is usually abbreviated as SCDP and becomes the central workplace for much of Mad Men.

The partnership develops after the original Sterling Cooper agency is sold to the British company Putnam, Powell & Lowe. Don and Roger object to the new ownership, while Bert Cooper joins their effort to establish a new firm. Lane Pryce provides crucial financial and administrative help, making the new agency possible.

SCDP begins with a small office and must compete for major accounts while building its reputation. Its name reflects the partners’ identities, unlike the earlier Sterling Cooper name. Later, SCDP merges with Ted Chaough’s Cutler, Gleason, and Chaough, creating Sterling Cooper & Partners. That later company is a different organization, which is why it should not be confused with the agency formed by the four original partners.