A graduate of Mizzou and the MU Law School, Dan was in Mizzou ROTC before serving four years in the United States Air Force. He served as a Captain in the USAF Judge Advocate General (JAG) Corp.

After leaving the Air Force, Dan returned to Columbia, where he practiced law and served as a community volunteer for more than 40 years. In October 2011, Dan was appointed by the governor to fill the vacant post of Boone County Presiding Commissioner. Boone County voters elected Dan in 2012 and re-elected him in 2014.

Dan is married to Karen Eads Atwill, with whom he will celebrate a Golden Wedding Anniversary in 2018. Dan and Karen have three children and seven grandchildren.