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Barack Obama appointed Kathleen Sebelius as the 21st Secretary of Health and Human Services on January 20, 2009. She was the first woman to hold this position and served in the role until January 20, 2017. Sebelius was a key player in the implementation of the Affordable Care Act (ACA), also known as Obamacare. She also oversaw the HHS response to the 2010 Deepwater Horizon oil spill.