MSNBC, a favorite among Democrats, lags behind. During the hearings, MSNBC averaged 2.7 million viewers.
On a typical day, Fox News has about 1.5 million viewers per day, and MSNBC is approaching 1 million, so viewing levels have certainly been raised by impeachment hearings.
It is clear that many people cared enough to get involved. They also wanted to see the spin later in the day – Fox's Hawk Hunt had one of its highest-rated shows of the year, with 4.4 million viewers.
It is impossible to estimate how many people have watched or listened to the hearings on all platforms, since television, radio and video streaming are measured in different ways.
Some people consume hearing in one seat, but the more common experience is much more widespread – listening to snipers in the air and watching social media clips and phone headlines.
But a much larger number of people have seen some of the hearings over the course of six hours. Nielsen's granular data shows fluctuations throughout the procedure.
For example, CNN averaged 1.85 million viewers during the entire hearing, reaching 11 midnight when more than 2.1 million were tuned in.
Wednesday's hearing was conducted live on PBS; by some local Fox stations; from S-SPAN; and other television networks.
And the debate was broadcast almost everywhere, on a wide variety of social networks and news websites.
CNN Digital reports strong, but not off the charts, interest in live testimony broadcasts.
There is no Nielsen-like way of measuring cumulative Internet viewing.
But overnight ratings suggest that the impeachment hearing has reached both a politically adverse and wider group of daily TV viewers.
However, the vast majority of Americans did not watch the entire event live – they dipped it on social media and later heard about it.