Bemoaning government policies but reveling in their newfound political prominence, Tea Party supporters filled Mellon Square with calls for change in Washington.

The lunchtime crowd was one of hundreds occurring across the country Thursday, marking the day federal taxes are due as well as a year of increasing activism and visibility by the conservative grass roots movement. Shortly after the one-hour rally, which was broadcast on radio station 104.7 FM, about 90 of the demonstrators boarded two buses, traveling to a similar demonstration in Washington D.C.

Rose Tennent, a commentator at the radio station, acted as emcee for the event and told the crowd, "We've been criticized for being angry ... there's such a thing as righteous anger, and I believe we've got it."

Bobbing above the crowd were scores of signs and placards with messages such as "Repeal, Impeach, Save America"; "As Government Grows, Liberty Decreases"; and "Change? We Got Tyranny."

Patti Weaver, a key organizer of the Pittsburgh Tea Party movement, warned the crowd against "infiltrators" and complained about media portrayals of extreme behavior at past Tea Party events. She branded as "a total lie" the accusations that some in a Washington demonstration had greeted African-American members of Congress with "the N-word" on the eve of passage of landmark health reform legislation.

But while the crowd cheered lustily at the repeated criticisms of the Obama administration, their mood, under bright sunshine, seemed more enthusiastic than angry.

Joanne Harvey of Scenery Hill, Washington County, stood smiling by the stage wearing a cap with the logo, "Reagan Library -- Air Force One." Dangling from it were six tea bags.

"It was really inspiring; I'm so happy I came," she said.

Before boarding a D.C.-bound bus after the event, Mrs. Weaver said that the group's energies would now be devoted to repealing the health care legislation and defeating members of Congress they see as champions of the liberal policies they oppose.

In addition to the health care bill, speakers criticized policies including bailouts of banks and auto companies and the proposed cap and trade legislation, which passed the House but appears stalled in the Senate.

Glen Meakem, the entrepreneur and radio show host, drew cheers as he read off a list of various state and local revenue sources and said, "Our taxes are way too high, and the Democrat Party is making them high."

He complained that governments squandered revenues, "building stupid government projects like the tunnel to the casino."

Despite Mr. Meakem's complaint, federal taxes on individuals have actually gone down since the Obama administration took office, chiefly through a variety of tax breaks enacted along with the administration's stimulus package. Taxpayers with higher incomes, however, will see a hike in their Medicare tax rate under the recent health care bill.

Elizabeth Lucas, the Pennsylvania director of administration-sponsored Organizing for America, said in a statement that the average tax refund had increased by an average of 10 percent since the stimulus legislation.

But analysts at all points on the political spectrum agree that without significant spending cuts, tax rates will be under increasing pressure from the deficits forecast for the coming decades.

Administration figures and many private economists contend that persistently high unemployment rates would be even worse without he effects of the federal stimulus policies. But Mr. Meakem heaped scorn on the administration policies, deriding "socialist Keynesian economics."

Mr. Obama, speaking Thursday night at a Democratic fundraiser in Miami, told supporters he is amused by the protesters' complaints about taxes because, contrary to their claims, he's cut taxes. "You would think they'd be saying thank you," the president said.

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