Hastert announced Thursday he is leaving Congress at the end of the year.
WASHINGTON (CNN) - In a brief speech tempered with reflection, former House Speaker Dennis Hastert, R-Illinois, announced his midterm resignation Thursday afternoon on the House floor.
"The time has come for me to make my last speech from this podium," he told his colleagues. "Our Founding Fathers envisioned a citizen legislature and it's time for this legislator to return to being a private citizen."
Peering up occasionally from his written speech, the congressman said, "I do hope that I have left a few footprints behind that may be of value to those who come after me - just as I have benefited from the footprints of those who I followed to this most wonderful of institutions, the People's House."
After his speech, the current speaker of the House, Nancy Pelosi, D-California, called Hastert honorable, "not just for the office he holds, but by virtue of his character, his leadership and his contributions to our country."
She added, "Thank you for your leadership, congratulations on a great career. God truly blessed America with your service."
Last month, two congressional GOP sources told CNN that Hastert, the longest-serving Republican speaker in history, would give up his congressional seat rather than serve out the remaining year of his term.
"I think he is just done with being a member of Congress," a GOP aide told CNN. Hastert did not give a specific reason Thursday for his resignation.
Over the summer, Hastert, 65, had said he would not seek re-election in the state's 14th District, which he has served for more than two decades. He became speaker of the House in January 1999, and stepped down after Democrats garnered the majority in the 2006 midterm elections, ending 12 years of GOP control.
An aide to Hastert said Thursday he will retire by the end of December.
In his Thursday address to the House, the former teacher and wrestling coach reflected on his long career in politics, listing health care, tax and Social Security legislation among his achievements.
More importantly, however, he said, was what he described as the representatives' "most solemn obligation": providing for the nation's defense.
"On Sept. 11, 2001, I became a wartime speaker and together we became a wartime Congress. On that dark day, our Congress was united - we were not Republicans or Democrats, we were just Americans. We stood shoulder-to-shoulder on the steps of this Capitol and vowed to do whatever was necessary," he said.
"We tried to bind the wounds of those victimized by the attacks."
"Did we get it 100 percent right?" he asked. "Of course not. Only hindsight is 20/20. But through those efforts, and the grace of God, we have avoided additional attacks on American soil."
Hastert's remarks on the attacks of Sept. 11 were met with loud applause.
The portly congressman also considered the "breakdown of civility in our political discourse," something he said he wishes he had been more successful in combating.
"We each have a responsibility to be passionate about our beliefs - that is healthy government - but we also have a responsibility to be civil, open-minded and fair - to listen to one another and work in good faith to find solutions to the challenges facing our nation," he said.
"That is why the American people sent us here. They did not send us here just to get re-elected."
Initially, Hastert's ascent to House leadership seemed unlikely. After Newt Gingrich stepped aside as House speaker following the GOP's dismal performance in the 1998 elections, Bob Livingston of Louisiana was tapped to replace him. But Livingston opted to leave Congress after revelation of an extramarital affair.
House Republican leaders then settled on Hastert - a man with virtually no national profile - for the No. 3 position in the U.S. government.
Hastert built a reputation as a formidable leader and by 2003 his Republican colleagues waived term limits to allow him to continue as their speaker.
His leadership came under scrutiny in 2006 amid the scandal surrounding fellow Republican Mark Foley's contacts with teenage congressional pages.
However, a House ethics report found that neither Hastert nor any other current lawmaker or staffer broke any House rules in handling allegations that Foley, a representative from Florida, was having improper communications with teenage male House pages.
Related video: Watch a clip of Hastert's farewell speech