Madigan made the surprise announcement even though she had previously said she plans to seek another term.
The popular attorney general was first elected in 2002. Her statement Friday did not include her future plans, which leave many people speculating.
Madigan will serve out her fourth term in office, serving since 2003. Her father, Illinois House Speaker Mike Madigan said he's proud of what his daughter has accomplished
In an interview with Lisa Madigan just Thursday, she offered no hints about her surprising decision not to run for re-election, a stunner that caught Democratic political insiders off guard.
"I just heard literally a second ago. Let me just say this just hearing about it, Lisa Madigan has a life of public service, one in which she should be proud of in the sense of her work," said Chicago Mayor Rahm Emanuel.
"I was really surprised that she decided not to move forward, but she did a great job for the people of Illinois and I just want to wish her well," said Illinois Secretary of State Jesse White.
In a written statement, Madigan says, "As I look ahead I believe that the end of my fourth term as attorney general will be the right time for me to seek a new challenge."
After serving as IL AG for over 14 years, I am announcing that I will not seek reelection. Read my statement here: https://t.co/LWmZ5lWPr8— Lisa Madigan (@LisaMadigan) September 15, 2017
Her political future is anybody's guess.
"I have not spoken to her, but I cannot speculate, where ever she decides to go she will bring a lot of knowledge, ability, energy and heart," said State Rep. Greg Harris, D-Chicago.
"She certainly hasn't closed the door, on some other year, some other time some other office," said State Rep. Barbara Flynn Currie. D-Chicago.
In a statement Friday, the Illinois Republican Party blamed the "toxic Madigan brand" for Lisa Madigan's exit. However, by her re-election numbers, the anti-Michael Madigan rhetoric has yet to extend to his daughter.
Madigan's announcement comes just hours after Illinois House Majority Leader Barbara Flynn Currie announced she is not seeking re-election after 40 years in office. Flynn Currie who is Illinois' longest serving majority leader and the first female says she can see Madigan as governor someday, or a run for U.S. Senate if Dick Durbin decides to retire in 2020. Some speculate the Illinois Supreme Court is also a possibility for Madigan.
"She is incredibly talented, she is young this is not a retirement party for Lisa Madigan," said State Senator Kwame Raoul, D-Chicago.
State Senator Kwame Raoul, who is considering running for Madigan's job says the popular attorney general is capable of any challenge.
"Lisa Madigan is not someone to shy away from any sort of battle," Raoul said.
Another Democrat considered to be a contender for Illinois Attorney General is Cook County Sheriff Tom Dart. Although Dart's top policy adviser said he is focused on his duties as sheriff, Dart expressed interest in Madigan's office in the past.
State Representative Emanuel Chris Welch has also been floated as a possible candidate. Welch said that he has been circulating a petition for reelection to his current office, but would talk to his family about a run for attorney general.
Republican candidate for Illinois Attorney General Erika Harold released a statement saying, "Illinois voters are tired of politicians putting the powerful political class ahead of the people. As I have traveled the state, I have heard over and over how career politicians have made it a nightmare for too many families in our state. Regardless of who the Democrats put forward, our campaign will continue to focus on protecting the people and not the powerful."
"I would like to thank Attorney General Lisa Madigan for her service to the people of Illinois and wish her the best in future endeavors."
Illinois House Speaker Michael Madigan said in a statement, "Throughout her life as an individual and as a public servant, Attorney General Lisa Madigan's achievements have been the result of her determination to fight for her convictions and to stand up for what she believed was right. I've always been proud of her desire to fight for those who need help the most, which has driven her sense of duty as a person and as Illinois' attorney general.
"It has been my privilege to watch her fight for the people of Illinois and do the right thing every day. She has authored tougher laws against criminals who prey on children and victims of sexual assault, fought for homeowners faced with losing their homes, and worked to ensure a more open and transparent state government.
"No father could be prouder of his daughter's personal and professional accomplishments, and I look forward to watching her continue her commitment to helping people in a new capacity."
Chicago Mayor Rahm Emanuel released a statement saying Friday, "Lisa Madigan's integrity, intelligence and unwavering commitment to justice made our state stronger and safer. Her service spans two decades and is one of many firsts. She is both the first female elected to serve as Attorney General of (Illinois) and the first (Illinois) Attorney General to argue a case before the Supreme Court in three decades. She never shied from criticism or shirked duty, earning her the esteem of colleagues, the respect of her critics and the admiration of the people of (Illinois). Despite earning national praise, Attorney General Madigan never forgot her South Side upbringing and fought for (Illinois). As a lawyer and lawmaker, she argued against discriminatory business practices, advocated for survivors of sexual assault and advanced access to affordable health care. While Attorney General Madigan may not be running for reelection, I am confident she will continue her selfless service beyond (Illinois), and I look forward to working with her in the years to come."
Lisa Madigan's full statement:
"After serving as Illinois Attorney General for over 14 years, today I am announcing that I will not seek reelection.
"I still have much work to do on many important issues, and I will continue to give my best to the people of Illinois and the Office of Attorney General every day through the end of my term in January 2019.
"As I look ahead, I believe that the end of my fourth term as Attorney General will be the right time for me to seek a new challenge. I have dedicated my career to helping people. That will continue to be my focus, and I am looking forward to finding new ways to do that with the passion that I have brought to my work as Attorney General.
"I have no doubt that having the opportunity to serve the people of Illinois as their Attorney General will forever be a highlight of my life. I thank the people of Illinois for placing their trust in me, and I want to thank all of those who have supported my work in elected office.
"As Attorney General, I've fought every day for the people of Illinois. I am particularly proud of:
Generating over $13 billion in revenue for the State;
Successfully arguing on behalf of Illinois in the U.S. Supreme Court;
Recovering over $3.2 billion in relief for homeowners, communities, and state pension funds from the mortgage crisis;
Saving Illinois utility ratepayers over $2.1 billion;
Helping over 43,000 identity theft victims remove over $29 million in fraudulent charges affecting credit reports and financial accounts;
Enforcing the environmental laws, fighting for strong regulations to combat global climate change, and advocating for environmental justice for communities impacted by pollution;
Strengthening the Freedom of Information Act and the Open Meetings Act and creating the first-ever Public Access Counselor in Illinois;
Legislating better protections for people living in nursing homes;
Shutting down predatory for-profit colleges and securing debt relief for their former students;
Exposing the fraudulent practices of student lenders and fighting for borrowers' rights;
Leading the nation in reforming the way law enforcement responds to sexual assault crimes, including training over 1,500 nurses to become Sexual Assault Nurse Examiners;
Championing a law to require Illinois colleges and universities to respond to sexual violence on campus, protect survivors' rights and provide a fair and balanced process to address complaints;
Successfully advocating to amend the Illinois Constitution to strengthen the rights of crime victims;
Overseeing the Illinois Internet Crimes Against Children Task Force (ICAC), which has been involved in the arrest of over 1,500 sexual predators, and investigating and arresting the most prolific child pornography traders in Illinois;
Educating over 573,500 parents and students on internet safety and 23,500 law enforcement members on investigating cybercrimes;
Prosecuting over 500 cases to ensure the most dangerous sex offenders are not released into communities;
Revoking the State's 10th casino license,
Successfully prosecuting local, county and state public officials across Illinois for misconduct; and
Initiating the State investigation of former Governor Blagojevich.
"Above all, I am proud of the countless ways that my office works every day to help people and protect their rights.
"I attribute our success to the hard work of the dedicated and talented lawyers and staff who I have the pleasure of working with in the Office of the Attorney General. I look forward to continuing my work as Attorney General and then taking on new, challenging opportunities at the end of my term."