William Morgan Cassidy (born September 28, 1957) is an American physician and politician serving as the senior United States senator from Louisiana, a seat he has held since 2015. A member of the Republican Party, he served in the Louisiana State Senate from 2006 to 2009 and in the U.S. House of Representatives from 2009 to 2015. Born in Highland Park, Illinois, Cassidy is a graduate of Louisiana State University (LSU) and LSU School of Medicine. A gastroenterologist, he was elected to the Louisiana State Senate from the 16th district which included parts of Baton Rouge, in 2006. In 2008, he was elected as the U.S. representative for Louisiana's 6th congressional district, defeating Democratic incumbent Don Cazayoux. In 2014, Cassidy defeated Democratic incumbent Mary Landrieu to represent Louisiana in the U.S. Senate, becoming the first Republican to hold the seat since Reconstruction. He was reelected in 2020. Cassidy was one of seven Republican senators to vote to convict Donald Trump of incitement of insurrection in his second impeachment trial. As a result, the Republican Party of Louisiana censured him. Early life and education William Morgan Cassidy was born in Highland Park, Illinois, one of four sons of Elizabeth and James F. Cassidy, and is of Irish and Welsh descent. He moved to Baton Rouge, Louisiana as an infant, and received a Bachelor of Science from Louisiana State University in 1979 and a Doctor of Medicine from LSU School of Medicine in 1983. Early career Medicine Cassidy specialized in the treatment of diseases of the liver at the Earl K. Long Medical Center (LSUMC). In 1998, Cassidy helped found the Greater Baton Rouge Community Clinic to provide uninsured residents of the greater Baton Rouge area with access to free health care. The Clinic provides low-income families with free dental, medical, mental health, and vision care through a "virtual" approach that partners needy patients with doctors who provide care free of charge. Cassidy has also been involved in setting up the nonprofit Health Centers in Schools, which vaccinates children in the East Baton Rouge Parish School System against hepatitis B and flu. In the wake of Hurricane Katrina, Cassidy led a group of health care volunteers to convert an abandoned K-Mart into an emergency health care facility, providing basic health care to hurricane victims. In 2010, Cassidy's alma mater, Louisiana State University, selected him for honoris causa membership in Omicron Delta Kappa,