(CNN) -- Rep. Jesse Jackson Jr. resigned from Congress effective Wednesday, citing the need to spend time "restoring my health."
Jackson, 47, announced his resignation in a letter sent to House Speaker John Boehner on Wednesday.
"For 17 years I have given 100% of my time, energy, and life to public service," Jackson wrote. "However, over the past several months, as my health has deteriorated, my ability to serve the constituents of my district has continued to diminish. Against the recommendations of my doctors, I had hoped and tried to return to Washington and continue working on the issues that matter most to the people of the Second District. I know now that will not be possible."
Jackson, 47, who has been treated for what he described last month as "several serious health issues," is the subject of several investigations.
Voters in his South Side Chicago district re-elected him for a 10th two-year term this month, despite his legal and health troubles.
"The constituents of the Second District deserve a full-time legislator in Washington, something I cannot be for the foreseeable future," he wrote to Boehner. "My health issues and treatment regimen has been incompatible with service in the House of Representatives. Therefore, it is with great regret that I hereby resign as a member of the United States House of Representatives, effective today, in order to focus on restoring my health."
Jackson, the son of civil rights leader the Rev. Jesse Jackson, is the subject of investigations by the FBI and House Ethics Committee.
His House colleagues are looking into allegations that, in 2008, he or one of his associates offered to raise money for then-Illinois Gov. Rod Blagojevich in exchange for Jackson being appointed to the Senate seat vacated by Barack Obama.
"During my journey I have made my share of mistakes," Jackson said in his resignation letter. "I am aware of the ongoing federal investigation into my activities and I am doing my best to address the situation responsibly, cooperate with my investigators, and accept responsibility for my mistakes, for they are my mistakes and mine alone. None of us is immune from our share of shortcomings or human frailties and I pray that I will be remembered for what I did right."
Illinois Gov. Pat Quinn has five days after the resignation is confirmed to set a date for a special election to fill the seat vacated by Jackson, the governor's spokesman said.
"As he works to address his health, our thoughts and prayers are with him, his wife Sandi, his children as well as his parents," House minority leader Nancy Pelosi said. "We are grateful to him and his family for their long-standing record of public service to our country."
Jackson has been out of the public eye and absent from Capitol Hill for much of the past year, including while he was being treated at the Mayo Clinic as recently as last month.
He made no campaign appearances, relying instead on a recorded automated call made to constituents in October in which Jackson said, "the good news is my health is improving, but my doctors tell me the road to recovery is a long one."
"Like many human beings, a series of events came together in my life at the same time and they've been difficult to sort through," he said in the call, which his office provided to CNN. "I am human, I am doing my best, and I am trying to sort through them all."
In early July, the congressman's office announced he was "receiving intensive medical treatment at a residential treatment facility for a mood disorder." A few weeks later, his office said he was undergoing an "extensive inpatient evaluation for depression and gastrointestinal issues" at the Mayo Clinic.
Jackson grew up in his father's shadow, placing him on history's stage as the Rev. Jesse Jackson Sr. led civil rights campaigns, including Operation PUSH and the Rainbow Coalition.
Jackson was born in 1965, just months before President Lyndon Johnson signed the Voting Rights Act, which forced election changes that opened up the political process for African-Americans in the United States.
He spent his 21st birthday in a District of Columbia jail cell after being arrested in an anti-apartheid protest at the South African Embassy in 1986, according to the biography on his congressional website.
He was on the stage in Cape Town in 1990 when Nelson Mandela delivered his historic speech after his release from 27 years in a South African prison, the biography says.
The younger Jackson earned a Master of Arts degree in theology and then a law degree in 1993.
He served as national field director for his father's Rainbow Coalition, a role that included leading the campaign to register millions of new voters, the biography says.
In 1995, the 30-year-old Jackson became the 91st African-American elected to Congress. Since then, he has represented Illinois' 2nd Congressional District, which includes parts of Chicago's