Some of the most prominent United States senators in 2015, defined by seniority, are Orrin G. Hatch, Patrick J. Leahy, Dianne Feinstein, Charles E. Grassley, Harry Reid, Barbara Boxer, Mitch McConnell and Thad Cochran. Patrick J. Leahy, a Democratic senator who represents Vermont, has the most seniority. He became senator on January 3, 1975.
The U.S. 114th Congress began on January 3, 2015. Each state has two senators, for a total of 100. Of the junior senators, the most senior is Barbara Boxer, a Democrat from California, who entered the Senate on January 5, 1993. The most junior senior senator is Deb Fischer of Nebraska, a Republican senator since January 3, 2013.