Now that I've been to Furnace Creek in Death Valley National Park, I believe I've ridden the highest paved road in North America and the lowest.
The highest paved road goes to the summit of Mount Evans in Colorado, at 14,240 feet.
For comparison purposes, the highest mountain in the "lower 48," Mount Whitney in California, is 14,505 feet. Mount Rainier is 14,411 feet. Mount Elbert, the highest in Colorado, is 14,443 feet. So Mount Evans is right up there!
Obviously the road is open only part of the year. And I'm sure you could experience snow year-round. My visit was on a hot (down below) August day, and it was cool and breezy at the top.
The pavement gets dicey toward the top, due to frost heaves, cracks, potholes, etc. - that's some harsh environment for Asphalt! And I had to slow for both bighorn sheep and mountain goats - lots of 'em. They charge a modest fee to take the road to the top.
The lowest paved road passes through Furnace Creek, in Death Valley, at 190 feet below sea level.
The lowest point in North America is in Death Valley, at -282 feet. So I'm confident the road passin' thru there is the lowest pavement.