Q: Context: The United States Department of Homeland Security (DHS) is a cabinet department of the United States federal government with responsibilities in public security, roughly comparable to the interior or home ministries of other countries. Its stated missions involve anti-terrorism, border security, immigration and customs, cyber security, and disaster prevention and management. It was created in response to the September 11 attacks and is the youngest U.S. cabinet department.

Question: what event led to establishing the department of homeland security answers.com? Let's give stream of consciousness first:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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To answer this question, we should know that: It was created in response to the September 11 attacks and is the youngest U.S. cabinet department. Therefore, the final answer is in response to the September 11 attacks.