Senator Robert C. Byrd served in the Senate for 51 years.
His office said he died about 3 a.m. at Inova Hospital in Fairfax, Va. Senator Byrd, who lived in McLean, Va., had been admitted to the hospital late last week with symptoms of heat exhaustion and severe dehydration as temperatures in the Washington area approached 100 degrees. Though he was initially expected to be released after a few days, his condition deteriorated. He had been in failing health for several years.
Mr. Byrd's death comes as Senate Democrats are working to pass the final version of the financial overhaul bill and win other procedural battles in the week before the Independence Day recess. In the polarized atmosphere of Washington, President Obama's agenda seemed to hinge on Mr. Byrd's health. Earlier this year, in the final days of the health care debate, the ailing senator was pushed onto the Senate floor in his plaid wheelchair so he could cast his votes.
Governor Joe Manchin III, a Democrat, will appoint an interim successor to Mr. Byrd.
Mr. Byrd served 51 years in the Senate, longer than anyone else in American history, and with his six years in the House, he was the longest-serving member of Congress. He held a number of Senate offices, including majority and minority leader and president pro tem.
