[13] In a candid interview with The Christian Science Monitor, Carl Sloane said "In the 1960s, if you had a Harvard MBA, a blue serge suit, and an air travel card, you were a consultant."

[19][20] In 1971, the chairman of the firm's board gave an expert testimony analyzing the impacts of the Energy Policy and Conservation Act based on Temple, Barker & Sloane's experience in the marine transportation industry.

"[21] In 1983, the firm was commissioned by the U.S. Department of Agriculture to investigate allegations of poor meat and poultry regulations by environmental activist Ralph Nader.

A spokesperson from the Agricultural Department confirmed that Temple, Barker & Sloane had a blanket contract for $100,000 and stated "We did ask them to look into the Nader charges and some other miscellaneous assignments...

"[22] After reading the firm's report, U.S. Representative Tom Harkin decided not to conduct hearings into Nader's charges, declaring that he was "satisfied the Reagan administration is not imperiling the nation's meat and poultry inspection program".

The purchase occurred during a time of consolidation in the industry, and pushed Marsh & McLennan back above Aon as the world's largest insurance broker.

[30][31] Throughout the 2000s, the company further transformed and focused its operating strategy through various acquisitions and divestment at its subsidiaries, including: In July 2017, Marsh & McLennan Cos. Inc. was ranked first in Business Insurance's world's largest brokers list.

[7] At the time of the 2001 September 11 attacks in the United States, the corporation held offices on eight floors, 93 to 100, of the North Tower of the World Trade Center.

In early 2005, Marsh agreed to pay $850 million to settle the lawsuit and compensate clients whose commercial insurance it arranged from 2001 to 2004.

[43] Much of Marsh & McLennan's corporate strategy since 2005 stemmed from an effort to recover from this tumultuous period, eventually leading to the firm's current organization and simplified focus on insurance services and consulting.