How far is the Kern River from Los Angeles?

Kernville, and the Wild and Scenic Kern River, is between 160 and 185 miles from Los Angeles depending on what route you take.
Driving North on Interstate 5 to Bakersfield and then taking highway 178 through the Canyon on the Lower Kern is the shortest drive in terms of distance.
The other popular option is to drive north on highway14 towards Lancaster and Ridgecrest. Before Inyokern, turn left on the 178 and wind through the mountains towards Kernville.

How far is the Kern River from San Diego?

Kernville, and the Wild and Scenic Kern River is between 280 and 300 miles from San Diego.
Drive North on the 15 and 215 towards San Bernardino before linking up with the 395 and pushing on to Inyokern. In Inyokern, take the 178 west through the mountains and into the Kern Valley. The other option is to take the 5 north towards LA and then choose whether to continue on towards Bakersfield on the 99 and the 178, or take the 14 North towards Lancaster and cut over on the 178 before reaching Inyokern.

Kernville, and the Wild and Scenic Kern River is about 50 miles from Bakersfield and takes a little over an hour.
It is an easy drive North on the 178 through the canyon of the Lower Kern. Taking the 155 outside of Lake Isabella will wrap you around the west side of the lake and into Kernville.

The Kern River is 294 miles from Las Vegas.
From Vegas take Interstate 15 West towards Barstow. Just past Barstow you will merge onto highway 58 for approximately 38 miles.
Turn onto highway 395 towards Ridgecrest.
Just before Inyokern you will turn onto highway 178 towards Lake Isabella and Kernville