The Alaska Highway starts in Dawson Creek, British Columbia. It continues through the Yukon Territory and officially terminates in Delta Junction, Alaska (although many people believe it ends in Fairbanks AK).
The Alaska Highway has undergone many improvements in past decades. Generally, it is good driving, with most of the highway being at least two lanes and paved.
The section of highway between Destruction Bay YT and the Alaska Border has many frost heaves. The best advice is to slow down and plan 4-5 hours if you're driving an RV through this section.
Regardless of the section of highway you're on, take your time and enjoy the scenery!