More than 10 million of those viewers watched Trump's speech on Fox News, according to a report by Adweek.
President Barack Obama's first speech to a joint session of Congress in 2009 drew 52.37 million viewers, according to Nielsen.
Trump's inauguration also drew fewer viewers than Obama's.
TV ratings: Trump inauguration came in behind Reagan and Obama pic.twitter.com/GKypP1zpH2
— David Taintor (@davidtaint) January 22, 2017
After networks aired side-by-side comparisons of the crowds at Trump's swearing-in compared to Obama's, the President and his staff spent the next week railing against the media for supposedly misrepresenting attendance.
Trump and members of his administration jumped at the chance to relitigate the subject at least eight times in the week after his inauguration, complaining about "very unflattering" photos taken "from certain angles" and accusing the media of "deliberately false reporting."