Following Route 20 (aka North Cascades Highway), which goes across the Cascades, the peak is at Sherman Pass (elev. 5,575 feet). If you're going to travel toward winter at all, you should check to make sure this route is open. If not, you will have to go a substantial distance in order to take a different route over the Cascades.
Get quick answers from North Cascades Highway staff and past visitors.