"It's nice to know, you know, there are folks out here who feel ... patriotic and thankful for what this country has done," said Joyce Harris, director of legislative and public affairs for the Bureau of the Fiscal Service. "It definitely does make you feel good."
On Tuesday, the latest debt ceiling fight ended with a whimper rather than a roar when Congress voted to approve the extension of the debt limit to 2015. The Senate is expected to take it up later in the week.
(Read more: House passes debt-ceiling increase withhout strings attached)
The lack of drama was refreshing reprieve from years of bickering about the level public debt, the debt ceiling and the federal budget.
(Read more: 4 ways to reduce your 2013 tax bill)
Harris said people offer up all sorts of reasons for donating to help reduce the public debt. Some donations come from students doing a civics lesson. Others come from veterans or immigrants who are thankful for the opportunities the country has given them. Sometimes people include donations in their wills.
"They want to give back," Harris said.
Some people give no reason at all for their donation, she added, especially if they are donating online.
(Read more: Why IRS customer service is awful and may get worse)
The donations vary by year but have generally stayed strong even through the Great Recession, weak recovery and bouts of bickering on Capitol Hill. The fiscal year that ended in September 2012 was especially robust, with more than $7.7 million in donations.
—By CNBC's Allison Linn. Follow her on Twitter @allisondlinn and Google or send her an email.