JayKay,
The public ramp is still available to launch your boat out of Alton Bay. After launching, you need to drop your trailer off about a mile away (there are good directions posted at the ramp)drive back to the launch area without your trailer attached and park your car. When you return, you drive your vehicle back to the trailer, hitch it up and return to the ramp area to retrieve your boat. If you want to pay $20.00 during the week, $25.00 on weekends, there is a Marina right before the bridge where you can launch and park from the same lot. Very convenient, but not free.
Good luck!
Bob