Surprised nobody's explained anything yet.
See the double-track SP crossing above the single-track WP?
http://www.bing.com/maps/?v=2&cp=qdxv0k ... orm=LMLTCC
The SP line is the Overland Route from Oakland to Roseville to Donner Pass to Chicago. The WP below is their main line from Oakland via Stockton, to Marysville and Oroville and then east up the Feather River to Nevada and Salt Lake City.
A little ways east of there is Elvas
http://www.bing.com/maps/?v=2&cp=qdxq5r ... orm=LMLTCC
where the SP line down the San Joaquin valley to Fresno (and beyond to Los Angeles and West Colton via Tehachapi Pass) meets the Overland Route.
At the east end of Roseville there's a wye
http://www.bing.com/maps/?v=2&cp=qfrtj6 ... orm=LMLTCC
where the SP line north to Portland leaves the Overland Route. It crosses the WP main near Marysville (a place called Binney Jct):
http://www.bing.com/maps/?v=2&cp=qhsmps ... orm=LMLTCC
South of Sacramento the sort-of-parallel SP and WP lines are both still in use to near Stockton
http://www.bing.com/maps/?v=2&cp=q9w5rb ... orm=LMLTCC
where the WP used to cross the SP but now runs onto it instead, with the WP main thru Stockton removed.
Speak up if you want more.