Who served as the Secretary of the Department of Homeland Security?

Janet Napolitano served as the Secretary of the Department of Homeland Security from 2009 to 2013 under President Barack Obama. She was the first woman to hold this position and played a significant role in shaping the department's policies and initiatives during her tenure. Her leadership included efforts to enhance security measures, respond to natural disasters, and manage immigration issues.

Other individuals listed in the options also served as Secretaries of Homeland Security, but at different times. Michael Chertoff was the second Secretary from 2005 to 2009 and is known for his work following the 9/11 attacks and the establishment of the department. Jeh Johnson served from 2013 to 2017 and focused on cybersecurity and immigration reform. Kirstjen Nielsen was the Secretary from 2017 to 2019 and dealt with issues surrounding border security and immigration policies during the Trump administration. Each played a role in the ongoing evolution of the Department of Homeland Security, but the specific period of Napolitano's service is a key aspect of her significance in this context.