Following the September 11, 2001 terrorist attacks, U.S. President George W. Bush named Ridge the first director of the newly created Office of Homeland Security.

Since reentering the private sector, Ridge has served on the boards of The Home Depot, The Hershey Company and Exelon Corporation and as a senior advisor to Deloitte & Touche and TechRadium.

He spent time campaigning with Senator John McCain during his 2008 presidential bid and was believed by some to have been on the short list of potential running mates.

Ridge's maternal grandparents were Rusyn immigrants[4] from the former Czechoslovakia (now Slovakia), and his paternal great-grandparents emigrated from Great Britain.

He attended Harvard College, where he paid his way through with construction work, played intramural baseball and football,[5] and graduated with honors in 1967.

[16] Over Ridge's tenure, the Commonwealth's budget grew by two to three percent per fiscal year and combined tax reductions totaled over $2 billion.

Ridge created and grew a "Rainy Day" Fund balance to over $1 billion to be utilized during an economic downturn or recession.

[17] Ridge pushed for legislation permitting competition among electric utilities and enhanced federal and state support for the Children's Health Insurance Program (CHIP).

[citation needed] Ridge oversaw a number of e-government projects including renewing drivers' licenses and vehicle registrations to viewing historical documents and library catalogs.

[19] Ridge signed two death warrants for African-American civil rights activist Mumia Abu-Jamal, who was convicted of killing a police officer at a traffic stop.

[22] Following the September 11, 2001, terrorist attacks, U.S. President George W. Bush created the Office of Homeland Security within the White House, and named Ridge to head it.

Ridge worked with the employees from combined agencies to strengthen borders, provide for intelligence analysis and infrastructure protection, improve the use of science and technology to counter weapons of mass destruction, and to create a comprehensive response and recovery division.

[23][24][25][26][27] In January 2004, Ridge was named among others in a lawsuit filed by a Syrian-born Canadian Maher Arar who said he was tortured in Syria after being deported by American authorities.

[28] On November 30, 2004, Ridge submitted his resignation to the President, saying, "After more than 22 consecutive years of public service, it is time to give personal and family matters a higher priority.

"[29] In his book The Test of Our Times: America Under Siege...and How We Can Be Safe Again, Ridge says his resignation was due to an effort by senior Bush administration officials to raise the nation's terror alert level in the days before the 2004 presidential vote.

[44] In 2009, antimicrobial company PURE Bioscience named Ridge, along with former Wisconsin governor Tommy Thompson, to its advisory board.

[53] In 2013, Ridge was a signatory to an amicus curiae brief submitted to the Supreme Court in support of same-sex marriage during the Hollingsworth v. Perry case.

[57][58] The Los Angeles Times reported a senior Clinton administration official as saying inclusion of the People's Mojahedin was intended as a goodwill gesture to Tehran and its newly elected president, Mohammad Khatami.

[61] Ridge and others wrote an article for the conservative publication National Review stating their position that the group should not be classified as a terrorist organization, raising the point that "The material-support statute doesn’t need revision to accommodate non-existent defects.

[63] In order to address biological threats facing the nation, the Blue Ribbon Study Panel on Biodefense created a 33-step initiative for the U.S. Government to implement.

Tom Ridge headed the organization with former Senator Joe Lieberman, and the Study Panel assembled in Washington, D.C., for four meetings concerning current biodefense programs.

He also said, during an interview with radio host Michael Smerconish, that it would be a "cold day in hell" before he "would consent to an uninvited, unilateral intervention" in one of his cities in Pennsylvania.

[67][68] Trump later slammed Ridge on Twitter, calling him "a failed RINO" and saying he "loved watching pathetic Never Trumpers squirm!".

He explains the challenges and decision-making processes of the newly formed department, and gives his own views as to the future of the security of the United States of America.

Among the headlines promoted by publisher Thomas Dunne Books: Ridge was never invited to sit in on National Security Council meetings; was 'blindsided' by the FBI in morning Oval Office meetings because the agency withheld critical information from him; found his urgings to block Michael Brown from being named head of the emergency agency blamed for the Hurricane Katrina disaster ignored; and was pushed to raise the security alert on the eve of President Bush's re-election, something he saw as politically motivated and worth resigning over.

[31]Ridge wrote in his memoir that then-Secretary of Defense Donald Rumsfeld and then-Attorney General John Ashcroft pressured him to raise the terror alert level, running up to the 2004 elections, because of a pre-election message critical of President Bush from Osama Bin Laden.