Peter H.B. Frelinghuysen Jr., an 11-term Republican congressman from New Jersey and a member of one of the state’s oldest and most prominent political families, died May 23 at his home in Harding Township, N.J., of respiratory failure. He was 95.

A Yale-educated lawyer, Mr. Frelinghuysen (pronounced Free-ling-high-zen) served in the U.S. House from 1953 to 1975 and is best remembered for helping block an effort to build what would have been the fourth large airport in the New York City area.

His district, which included wealthy, semirural Morris and Somerset counties in northern New Jersey, is currently represented by his son Rodney, a Republican first elected in 1994.

Four U.S. senators and two congressmen have been Frelinghuysens. The family traces its roots to a leader in the Dutch Reformed Church who settled in New Jersey about 1720.

Family members have served in politics since the 18th century. Peter Frelinghuysen was the great-great-great-grandson of Frederick Frelinghuysen, a New Jerseyite who became a U.S. senator in 1793 after serving as delegate to the Continental Congress, the American colonies’ governing body during the Revolutionary War.

Peter Frelinghuysen was a moderate Republican who supported the landmark 1964 Civil Rights Act but opposed President Lyndon B. Johnson’s War on Poverty, saying the raft of federal programs would “spawn its own bureaucracy.”

Despite favoring small government, he was a champion of spending federal dollars on school construction. As the ranking member of the Education and Labor Committee, Mr. Frelinghuysen’s voting record was “quite near center,” wrote Washington Post political reporter Richard L. Lyons in 1965, “and not offensive to either wing.”

Mr. Frelinghuysen attempted to join the Republican leadership in 1965, when he ran for party whip. Despite an endorsement from newly elected House minority leader and future president Gerald R. Ford, he lost to Leslie C. Arends of Illinois, who had been whip since 1943 and developed a reputation as a jovial and highly effective party loyalist.

“To win over such a candidate, Mr. Ford needed a dynamic legislator of wide reputation and high standing among his colleagues,” a Post editorial said. “Mr. Frelinghuysen, a middle-roader from New Jersey, failed to make the grade.”

When he retired in 1975, the congressman was perhaps most widely known for his role in protecting what is now the Great Swamp National Wildlife Refuge, an enclave of woodlands and marsh in Morris County about 25 miles west of New York City.

The area was slated to become an international airport, according to plans made public in 1959 by what is now the Port Authority of New York and New Jersey. Mr. Frelinghuysen, who lived on a nearby estate, led neighbors and conservationists in a successful fight to stave off development.

A fundraising effort raised more than $1 million to help an environmental group purchase almost 3,000 acres of the threatened parcel. That land became the heart of the Great Swamp refuge, established by an act of Congress in 1960.

Peter Hood Ballantine Frelinghuysen Jr. was born in New York on Jan. 17, 1916. His father was a banker and horse breeder, and his mother was an heiress to a sugar fortune.

Mr. Frelinghuysen graduated from Princeton University in 1938 and from Yale Law School in 1941. He served in the Office of Naval Intelligence during World War II and worked in banking and finance before he was elected to public office.

His wife of 55 years, Beatrice Procter Frelinghuysen, died in 1996.

Besides his son Rodney, of Morristown, N.J., survivors include four children, Beatrice Frelinghuysen van Roijen of Washington, Adaline H. Frelinghuysen and Peter Frelinghuysen, both of New York, and Frederick Frelinghuysen of Tucson; 13 grandchildren; and nine great-grandchildren.