Original: In January 2003, the office was merged into the Department of Homeland Security and the White House Homeland Security Council, both of which were created by the Homeland Security Act of 2002.
Simplified: In 2002, because of the September 11 attacks in 2001, Congress passed a bill called the Homeland Security Act, which created the Department of Homeland Security. Tom Ridge was the first leader of the Department of Homeland Security.