The country performed 1,061,411 tests on Saturday, according to data from The COVID Tracking Project, a volunteer-run effort to track the outbreak.
The record comes after testing has fallen for several weeks. The United States tested on average 650,000 people a day in the week ended Sept. 13, down from a peak in late July of over 800,000 people a day.
Since the start of the pandemic, testing shortages have hampered efforts to curb the spread of the virus.
At one point during the summer, Houston residents lined up in cars and waited hours for tests, even sleeping in their vehicles overnight. Miami saw similar lines.