Pennsylvania Lt. Gov. Catherine Baker Knoll, who was the first woman to be elected in that position, died Wednesday after battling cancer. She was 78.

Knoll died at National Rehabilitation Hospital in Washington, D.C., Gov. Ed Rendell said. She was diagnosed with neuroendocrine cancer in July and recently developed a viral infection after undergoing radiation and chemotherapy treatments.

"Catherine was a wonderful person and that really made her a fine public servant, both as state treasurer and lieutenant governor," Rendell told The Associated Press. "She cared as deeply about people and the problems they faced as much as any public official who served the commonwealth."

Knoll returned to work as the Senate's presiding officer at the start of the fall Senate schedule in September, but showed signs of fatigue. Later that month, she said she would take time off on the advice of doctors and family.

A former schoolteacher and Democratic veteran, Knoll won two terms as state treasurer, in 1988 and 1992. In 2003, she beat out eight other candidates in the Democratic primary for lieutenant governor, and went on to win the office as Rendell's running mate.

Rendell said Knoll's broad constituency and name recognition had helped him appeal to her home turf of western Pennsylvania. She was fond of saying her age had brought wisdom, and that she needed no on-the-job training.

"I happen to think that Pennsylvania is like a 10-speed bicycle," Knoll said on the day she was sworn in in 2003. "We have gears we haven't even tried yet."

As lieutenant governor, she held the gavel in the state Senate and chaired the state Board of Pardons, her primary tasks.

Under the state Constitution, Knoll will be replaced by the Senate President Pro Tempore, Joseph B. Scarnati III, R-Jefferson, who plans to retain his Senate seat.

In a statement, Scarnati said Knoll "embodied the type of character expected of true, effective public servants."

U.S. Sen. Bob Casey called her life "one of service and sacrifice, courage and commitment to the common good."

Knoll's tenure as treasurer had been damaged by allegations that a former campaign aide used his position to benefit from the sale of state bonds. Knoll was never implicated, but it came up repeatedly in later campaigns.

Aside from her long service, Knoll was known for raising eyebrows with an occasional gaffe.

In 2005, Knoll apologized to the family of a Marine killed in Iraq for showing up uninvited for his funeral and giving out a business card. Rendell said her action was a mistake of the heart by someone who wanted to be called if she could alleviate suffering or ease burdens.

Also that year, she introduced an Amazon parrot to the Senate floor. The parrot, from the national Aviary in Pittsburgh, warbled "How much is that doggie in the window?" for stunned lawmakers, some of who were angered by what they viewed as a breach of protocol.