The New York senator addressed rallies in Hillsboro, where supporters began arriving two hours before Clinton was scheduled, and Eugene, The Oregonian reported.
At South Eugene High, an audience of 2,500 heard Clinton speak on topics ranging from jobs to healthcare to Iraq, The Register-Guard reported.
"It took a Clinton to clean up after the first Bush," she said, mentioning her husband, former President Bill Clinton in a line drew applause. "It's going to take a Clinton to clean up after the second Bush."
She accused the current administration of misusing and suppressing scientific information.
In a question-and-answer session at one stop, a man who said he supported Illinois Sen. Barack Obama asked Clinton if she or her supporters have said or done anything that would weaken Obama in November if he is the nominee.
She said the campaign has been "one of the most positive" she has ever been a part of, CBS News reported. She said an election "is not a coronation, it is a contest, this country is worth fighting for, and I'm going to fight for it."
The Oregon primary is set for May 20.