Highway 4 is 197 miles long from Hercules at the western end to Markleeville in the eastern end. I haven't driven the whole way, only about 50 miles of it. But so far my favorite has to be the stretch from Hercules to the Alhambra exit in neighboring city of Martinez.
Why you ask? Just see.
The western end hits Interstate 80 in Hercules. One of my goals/dreams/bucket list items is to drive I-80 to Chicago, where if my map reading is correct is where the interstate ends.