Established as a state on December 12, 1787—the second state to join the Union—Pennsylvania became the first state to elect U.S. senators. William Maclay and Robert Morris, elected on September 30, 1788, took office on March 4, 1789. Pennsylvania’s longest-serving senators include Boise Penrose (1897–1921) and Arlen Specter (1981–2011). Among those who rose to leadership positions are Hugh D. Scott, who served as Republican leader, and Rick Santorum, who served as Republican Conference chairman. As vice president from 1845 to 1849, George M. Dallas was the Senate’s constitutional president or presiding officer.