Utility companies brought in additional crews, but authorities said it could be days, or even up to a week, before all the power is restored.
The storm is also being blamed for at least 12 deaths. Six people died in Pennsylvania alone.
The rare October storm brought more than a foot of snow in some areas, leading four states to declare a state of emergency.
Trees, branches and power lines still littered roads and rail lines, leading to a tough Monday morning commute for many. Hundreds of schools canceled classes.
Some local officials canceled or postponed Halloween activities, fearful that young trick-or-treaters could wander into areas with downed power lines or trees ready to topple over.
Temperatures are expected to begin rising Monday and the snow will start melting, the National Weather Service said.
The Associated Press contributed to this story.