Near where I live is Lick Skillet Road. It's a dirt road that shoots off of one of the most popular canyon rides nearby. According to Wikipedia, it's the steepest county road in the US. I *think* it covers 1000 vertical feet in 1 mile, that would make it 18.9%. The thing is it's nearly completely straight, going from the town of Gold Hill straight down to the paved canyon road. I'm sure there is an interesting story behind the name, but I don't know what it is and my brief google search didn't turn up any relevant information.