Nick Kotz, who won a Pulitzer Prize in 1968 for exposing unsafe and unsanitary conditions in the nation’s meatpacking plants and who later became a Washington Post reporter and the author of books investigating hunger, civil rights and military contracting, died April 26 at his home near Broad Run, Va. He was 87.

According to a statement from the Virginia State Police, Mr. Kotz stopped his car in his driveway to retrieve an item from the back seat. The car rolled backward, striking him. He died at the scene.

Mr. Kotz, a well-known figure in Washington’s journalism circles for more than 50 years, was in his 30s when he won a Pulitzer while working in the Washington bureau of the Des Moines Register.

In 1967, he wrote more than 50 articles about poorly regulated meatpacking plants. He showed that, contrary to common belief, plants that did not engage in interstate commerce — about a quarter of the nation’s total — were not subject to federal inspection.

Conditions in many of those plants, Mr. Kotz found, were as dangerous and unsanitary as they had been at the turn of the 20th century, when muckraking reporter and novelist Upton Sinclair wrote about the deplorable state of the country’s slaughterhouses in his 1906 novel “The Jungle.”

As a result of Mr. Kotz’s investigations, Congress passed the Wholesome Meat Act of 1967, requiring all meatpackers and manufacturing companies to adhere to the same federal standards.

Mr. Kotz was invited to the White House to witness President Lyndon B. Johnson signing the bill into law. Also attending the ceremony was the 89-year-old Sinclair, more than 60 years after he had published “The Jungle.”

“By almost any measure of journalistic excellence,” consumer advocate Ralph Nader said in 1968, “Mr. Kotz came through with a classic performance of objectivity, timeliness, stamina and thorough coverage.

“If there is ever any need to demonstrate how investigative journalism can break through the elaborate obstructions to information flow on the part of both government and industry, the writing[s] of Mr. Kotz on the unwholesome meat situation will stand as memorable beacons.”

During his years with the Register, Mr. Kotz also reported on patronage in the U.S. Postal Service and about the trucking industry’s influence on Congress. Advertisements in the newspaper featured a picture of Mr. Kotz, with the line: “Nick Kotz of The Des Moines Register’s Washington Bureau isn’t afraid to point the finger at injustice and those responsible for it.”

He joined The Post in 1970 as a national reporter and worked on several investigative series on civil rights, labor unions and other topics. He contributed to coverage of the Watergate scandal before leaving The Post in 1973 to pursue independent writing projects.

His books included “Let Them Eat Promises: The Politics of Hunger in America” (1969); “The Unions” (1972), written with Post reporter Haynes Johnson, about corruption in labor unions; “A Passion for Equality” (1977), written with his wife, Mary Lynn Kotz, about scientist and civil rights activist George Wiley; and “Wild Blue Yonder: Money, Politics, and the B-1 Bomber” (1988), describing what Mr. Kotz called “a defense system that is spinning madly out of control” with fraud, waste and self-dealing.

In 2005, Mr. Kotz published “Judgment Days,” an account of how the sometimes strained relationship between Johnson and the Rev. Martin Luther King Jr. led to the enactment of sweeping civil rights laws in the 1960s.

“It captures Johnson and King at the apex of their collaboration, a snapshot of an optimistic peak that only magnifies the friction and tragedy to come,” journalist Samuel G. Freedman wrote in a review in the New York Times. “And it typifies the meticulous research, restrained prose and deep appreciation of motivation and character that make ‘Judgment Day’ a stirring, indeed heartbreaking, book.”

Mr. Kotz was born Nathan Kallison Lasser in San Antonio on Sept. 16, 1932. His parents split up soon afterward, and he grew up with his mother and grandparents.

Nick — as he was called from an early age — moved to Washington in the mid-1940s, when his mother remarried. He was adopted by his mother’s second husband, Jacob Kotz, a physician and medical school professor. His mother, Tibe Kallison Kotz, later became the president of real estate company.

Mr. Kotz was a 1951 graduate of Washington’s private St. Albans School, where he was a member of the golf and football teams. He graduated with honors from Dartmouth College in 1955, then did graduate work at the London School of Economics. He served as a Marine Corps officer before joining the Des Moines Register in 1958. He moved to the paper’s Washington bureau in 1964.

Mr. Kotz contributed to many publications over the years and taught journalism at American University. He was the primary author, assisted by several of his students, of a 1984 Washingtonian article, “Where Have All the Warriors Gone?,” about a cultural clash among military leaders, that won a National Magazine Award.

Mr. Kotz lived in Chevy Chase, Md., before moving to a farm in Fauquier County, Va. In the 1990s, he and his wife helped lead opposition to a proposed Disney theme park near Haymarket, Va. The idea was eventually abandoned.

Survivors include his wife of 59 years, the former Mary Lynn Booth, a journalist and author, of Broad Run; a son, Jack Kotz of Santa Fe, N.M.; and a grandson.

In his final book, “The Harness Maker’s Dream” (2013), Mr. Kotz chronicled the life of his grandfather, a Jewish immigrant who became a prominent businessman and rancher in Texas.

As a child, Mr. Kotz wrote in an essay in Kirkus Reviews, “I knew more about Sam Houston and his victory in the Texas War of Independence from Mexico than I did about my own grandparents’ escape from a different revolution in Russia.”

His grandfather, Nathan Kallison — for whom Mr. Kotz was named — was a harness maker who made his first land purchase in Texas in 1902. He signed the contract in Hebrew script; his wife signed with an X. For decades, Kallison’s of San Antonio was the largest farm and ranch supply store in the Southwest.

Working on “The Harness Maker’s Dream,” Mr. Kotz later told Washington Jewish Week, “changed my perspective on how to look at American history.

“As a reporter, my focus was on the big events, looking from the top. Having done the book, I’ve learned that I can best understand the country’s history by looking at the lives of ordinary people.”