When Milton Moskowitz set out to evaluate America’s best companies to work for, he took a novel approach: He talked to their employees.

He and a colleague, Robert Levering, spent more than a year traveling the country, interviewing hundreds of workers in dozens of cities. The resulting book, “The 100 Best Companies to Work For in America,” was a best seller when it was published in 1984, and it laid the groundwork for similar lists, both by Mr. Moskowitz and by imitators around the world.

“A good workplace,” he wrote in The New York Times in 2007, “is one where management trusts the employees and where employees trust the management.”

Mr. Moskowitz died on March 5 at his home in Mill Valley, Calif. He was 91. His brother, Gerald, confirmed the death.