Unlike the other seven soon-t0-be-retired House committee chairs, however, Frelinghuysen wasn't facing the term limits House Republicans place on gavel-holders: He just took over the powerful Appropriations Committee in 2017.
Frelinghuysen, who assumed office in 2011, faced a competitive race to retain his seat in his northern New Jersey district.
The district leans Republican, but President Donald Trump only beat failed Democrat presidential candidate Hillary Clinton by less than a percentage point. With the federal government fast approaching another financial deadline, Frelinghuysen said he was "determined" to finish the appropriations bills for the current fiscal year and pass next year's bills "through regular order".
"I have worked in a bipartisan manner, not just in times of crisis but always, because I believe it best serves my constituents, my state and our country", he said. "My father reminded me often that we are temporary stewards of the public trust". He then served in the Continental Congress, as a member of the New Jersey convention that ratified the Constitution, and later in the U.S. Senate.
But one of his constituents painted a different picture in a conversation with ThinkProgress Monday.
In May, Frelinghuysen wrote a letter to a local bank calling employee Saily Avelenda a "ringleader" in the activist group NJ 11th for Change, some of Frelinghuysen's harshest critics.
"In one of the meetings, the building we were supposed to meet in was blown up before we could meet there, and it became so unsafe with so many threats that we were going to have to call it off", Granger said of that project at a Women, Peace and Security Symposium at the George H.W. Bush Presidential Library in December. With vote after vote, we were betrayed.
Rodney Frelinghuysen, 71, practically grew up in Washington because his father, Peter Hood Ballantine Frelinghuysen Jr., served 11 terms in the House, from 1953 to 1975. Nonpartisan analysts say Democrats have a good chance to grab it in this year's midterms.
"Today as I announce my retirement at the end of this session of Congress, I want to use the opportunity to strongly encourage the many young people I meet to consider public service".
Frelinghuysen's lackluster third quarter fundraising - he pulled in only $157,000, notably low for an appropriations chairman from an affluent district - inspired plenty of retirement rumors.
The 12-term Republican has also been critical of some of Trump's policies, including his proposal to ban some people from Muslim countries from coming into the U.S. But he had still largely voted in line with the president and his party, spurring protests in his district from activists after he supported a bill past year to repeal and replace the Affordable Care Act.
The strangest thing about the timing is that Republicans have been showing signs of life on the generic ballot lately thanks to the growing popularity of tax cuts.