Edward's great post got me looking up population DENSITY for the CBSAs in California. Here's a summary from 2010 Census data, with some minor rearranging so regions are kept together and identified by the MPOs (which control transportation $$) covering them. The highest density CBSA in a region determines the ranking of the region in the overall list. Also included some other big metro areas especially those that have a reputation for being transit-friendly, and the standard national averages.

A few highlights that grabbed me:
* Portland OR & Sacramento CA are almost the same size. Sacramento has a higher overall density. Why is Portland the OMG Great Transit city and Sacramento is barely there? Yes, I know we have Prop 13 and they don't ...
* Despite the huge differences in land area and population, LA-LB-(Orange County) is nearly the same density as the central SF Bay Area. And despite the general assumptions about LA and transit, that central area (LA and Orange Counties) does have a fairly dense transit network; main problems are the distances involved (Oakland might be 1/2 hour (maybe 10 miles) from San Francisco on the bus, but it's hard to even get out of Orange County in 1/2 hour (20-30 miles) on a bus), and the multiple different operators and systems, sometimes with overlapping service areas, that don't always connect as well as they should.
* Check out how San Jose nearly matches Chicago for density (dueling 'burbs??) and both are higher than Boston. Why the differences in transit availability?
* Salinas is higher density than DC?? Not sure how that happened, even given that the Monterey area is part of the CBSA. Was Fort Ord still operating in 2010 (counting platoons)? Lots of labor camps?
* San Joaquin Valley in general is low density for CA, but Stockton beats Seattle, and Stockton and Modesto both beat Portland OR. Fresno isn't far behind. And check out those total population numbers with both Fresno and Bakersfield pushing a million in 2010; what do you think happens there when HSR places them within 1-2 hours of LA and SF? And even at the low end, Madera is almost double the national average density for CBSAs of its population.
* In fact, nearly all the California CBSAs have higher population densities than the national averages for their size. Depends on your numbers, though: I saw something a couple of years ago that used a different analysis method and concluded that the LA Metro Area (the whole Basin, including San Bernardino, and the high desert commute zones) had a higher density than the New York metro area including Connecticut. Our suburbs apparently have more houses per acre than theirs ... which ultimately overcomes the Manhattan density mountain.

All are listed as: CBSA: population; density (persons/sq mile)

New York-Northern New Jersey-Long Island, NY-NJ-PA Metro: 18,897,109; 31,251.4

Average of U.S. metro areas of 5,000,000 or more: 8,431,848; 13,328.3

San Francisco Bay Area (MTC/ABAG)
San Francisco-Oakland-Fremont, CA Metro Area: 4,335,391; 12,144.9
San Jose-Sunnyvale-Santa Clara, CA Metro Area: 1,836,911; 8,417.7
Vallejo-Fairfield, CA Metro Area: 413,344; 4,502.1
Napa, CA Metro Area: 136,484; 4,045.9
Santa Rosa-Petaluma, CA Metro Area: 483,878; 3,253.6

Los Angeles Region (SCAG)
Los Angeles-Long Beach-Santa Ana, CA Metro Area: 12,828,837; 12,113.9
Oxnard-Thousand Oaks-Ventura, CA Metro Area: 823,318; 5,542.2
Riverside-San Bernardino-Ontario, CA Metro Area: 4,224,851; 4,299.6
El Centro, CA Metro Area: 174,528; 3,062.6

Chicago-Joliet-Naperville, IL-IN-WI Metro Area: 9,461,105; 8,613.4
Boston-Cambridge-Quincy, MA-NH Metro Area: 4,552,402; 7,980.1

San Diego Region (SANDAG)
San Diego-Carlsbad-San Marcos, CA Metro Area: 3,095,313; 6,920.5

North Central Coast Region (AMBAG)
Salinas, CA Metro Area: 415,057; 6,402.3
Santa Cruz-Watsonville, CA Metro Area: 262,382; 4,553.7

Washington-Arlington-Alexandria, DC-VA-MD-WV Metro Area: 5,582,170; 6,388.1

Average of all U.S. metro areas: 705,786 6,320.8

South Central Coast Region (SBCAG, SLOCOG)
Santa Barbara-Santa Maria-Goleta, CA Metro Area: 423,895; 6,242.8
San Luis Obispo-Paso Robles, CA Metro Area: 269,637; 2,293.4

Average of U.S. metro areas of 2,500,000 to 4,999,999: 3,522,237; 5,549.9

San Joaquin Valley (SJCOG, STANCOG, MCAG, MCTC, FCOG, KCAG, TCAG, KCOG)
Stockton, CA Metro Area: 685,306; 4,889.1
Modesto, CA Metro Area: 514,453; 4,322.7
Fresno, CA Metro Area: 930,450; 4,216.1
Bakersfield-Delano, CA Metro Area: 839,631; 3,711.5
Hanford-Corcoran, CA Metro Area: 152,982; 2,996.2
Visalia-Porterville, CA Metro Area: 442,179; 2,804.1
Merced, CA Metro Area: 255,793; 2,455.0
Madera-Chowchilla, CA Metro Area: 150,865; 2,391.0

Seattle-Tacoma-Bellevue, WA Metro Area: 3,439,809; 4,721.6

Sacramento Valley (SACOG, BCAG, ShCOG)
Sacramento--Arden-Arcade--Roseville, CA Metro Area: 2,149,127; 4,538.5
Yuba City, CA Metro Area: 166,892; 2,206.1
Chico, CA Metro Area: 220,000; 2,144.7
Redding, CA Metro Area: 177,223; 1,334.2

Portland-Vancouver-Hillsboro, OR-WA Metro Area: 2,226,009; 4,372.6

Average of U.S. metro areas of 1,000,000 to 2,499,999: 1,631,131; 3,489.4
Average of U.S. metro areas of 500,000 to 999,999: 699,135; 2,985.5
Average of U.S. metro areas of 250,000 to 499,999: 350,299; 2,321.4
Average of U.S. metro areas of less than 250,000: 147,527; 1,597.0

And you're right, I almost certainly won't be around in 2040, but the kids probably will be. Dealing with many more people, hotter weather, less rain, and higher sea level, but around. I wish them luck, and a transportation system that still works even with hiccups.