[2][3][4] In October 2023, WPP announced yet another merger in which Wunderman Thompson, along with another group agency VMLY&R, would cease to exist and create a new combined entity named VML.

[6] Founder William James Carlton started selling advertising space in religious magazines, but almost nothing is known about the partner named Smith.

The New York Times wrote that "the agency traces its roots to a newspaper space brokerage that began operation on December 5, 1864.

[9] Thompson, who had served as a U.S. Marine during the Civil War, had first been employed by Carlton & Smith to sell space in religious publications.

[11] In the mid-1970s, J. Walter Thompson was hired by the military dictatorship of Chile, led by Augusto Pinochet, to "refurbish the image of the regime" after international and Chilean human-rights organizations had documented extensive violations.

[25] It was also the first agency to provide a wide range of advertising services to clients, including copy, layout, package design, trademark development and rudimentary, market research.

[25] Many of these methods can be seen in notable work that the agency has produced, including work for Kraft Cheese that resulted in the creation of the grilled-cheese sandwich, a campaign for Swift & Co. that added measurement marks to sticks of butter, the Toys "R" Us Kid slogan and jingle, De Beers diamond ads ("A Diamond is Forever") and the "I wish I were an Oscar Mayer Wiener" campaign.

[28] The New York Times reported that "some two million other documents ... (are) .. within the J. Walter Thompson Archives at Duke University in Durham, North Carolina.

In June 2018, then CEO, Gustavo Martinez officially parted ways with J. Walter Thompson (JWT) and parent company WPP two months after settling a sexual harassment case brought by a female colleague.