Tom Ridge, the nation's first homeland security secretary, announced Tuesday that he is resigning after three years of reworking American security and presiding over color-coded terror alerts. He's the seventh Bush Cabinet officer leaving so far.

Ridge oversaw the most significant government reorganization in 50 years. He'll be remembered for his terror alerts and tutorials about how to prepare for possible attacks, including the controversial "disaster kits" that caused last year's run on duct tape and plastic sheeting.