The protest began around 11:30 am, interrupted briefly when Rep. Ted Poe, R-Texas, tried to start the House's work at noon. The customary prayer and pledge of allegiance went ahead, but Poe was forced to recess the House when dozens of Democrats refused to leave the well.
By late afternoon, 168 House Democrats — out of 188 — and 34 Senate Democrats joined the protest, according to the House minority leader's office, and there was no sign of quitting.
Congress remains gridlocked over gun control, a divide even more pronounced in a presidential election year. The sit-in had the feel of a 1960s-style protest, as some lawmakers sat on the floor, others in their seats.
Rep Bobby Rush of Illinois said he was proud of his fellow Democrats and offered a rebuke to Ryan and other GOP leaders, who were absent from the chamber most of the day.
"You can run, but you can't hide," Rush said to cheers from his Democratic colleagues.
Republicans had staged a similar protest in 2008. Democrats controlling the House at the time turned off the cameras amid a GOP push for a vote to expand oil and gas drilling. Republicans occupied the floor, delivering speeches after then-Speaker Nancy Pelosi sent the House on its August recess. Pelosi ordered the cameras turned off.
Republicans ultimately forced the drilling provision to be attached to a stopgap spending bill.
C-SPAN, a cable and satellite network that provides continual coverage of House and Senate floor proceedings, does not control the cameras. They're run on authorization by legislative leaders.
Although the cameras were turned off Wednesday, lawmakers relied on social media to transmit video, using Facebook, Twitter and Periscope.