Solvang (September 3, 2019):
Baker
Los Angeles
Monterey
San Diego
San Francisco
Saint Joseph
Saint Louis the Bishop
Santa Barbara
Solvang
They're not from California, but I'm adding them because we also did them on this trip:
Grand Canyon (Arizona)
Las Vegas (Nevada)
Tijuana (Baja California, Mexico)
Solvang's history in a few lines:
Origins:
The area where Solvang is located today was originally inhabited by the Chumaš, an Indigenous people who occupied the central coast of California for thousands of years. Their presence left traces in routes, villages, and economic activities linked to the natural environment.
Middle Ages:
There is no equivalent Middle Ages in this territory; while Europe was developing medieval structures, the region continued to be inhabited by indigenous communities such as the Chumaš, with their own social systems and far removed from European development.
19th Century:
After California's incorporation into the United States in 1848, the area was primarily used for farming and ranching. At the beginning of the 20th century, Danish immigrants sought a place to establish an educational and cultural community, which laid the groundwork for the future founding of Solvang.
Present:
Solvang was officially founded in 1911 by Danish settlers and is now known for its distinctive Nordic aesthetic, Danish-style architecture, traditional bakeries, windmills, and cultural festivals. It is a prominent tourist destination within Santa Barbara County and a symbol of the Danish legacy in California.
It's not a very big town, but it's quite pretty. It's worth stopping to take some photos, although you have to go early because everything closes at 5 pm. It's a street dedicated to small souvenir shops, and they're not cheap at all.
Solvang combines very well with Santa Barbara for its proximity and for combining coast, charming towns and quiet routes through California.
Information obtained from the web https://www.exteriores.gob.es
Passport: It must be electronic and have a minimum validity of 6 months from the date of entry into the U.S. and at least two blank pages. The passport must have been issued after 2006.
ESTA form: Spanish citizens must complete the ESTA (Electronic System for Travel Authorization) form at least 72 hours before their flight. This allows stays of up to 90 days without a visa. 40,27$/Person. LINK.
Return ticket: You must present a return ticket dated within 90 days to prove that you will leave the country within that time.
Travel insurance: It is recommended to have adequate travel insurance due to the high cost of medical care in the USA. In our case, we always used Iati, but lately we've been using Globalfine, which is much cheaper.
Vaccines: There are no mandatory vaccinations for entry.
Special conditions: If you have traveled to certain countries, such as Cuba, Iran, or Syria, after specific dates, you may need a visa instead of an ESTA.
International driving permit: It is requested through the website of the DGT.
It costs €10.51. The good thing is you can order it online and pick it up without an appointment. It took a couple of days for ours, then you go to pick it up and it's a cardboard card like the ones they had 20 years ago.
Travel insurance: It is recommended to have road insuranceHeh. The best known and most complete ones are Iati y Heymondo, if we don't need insuranceWe'll grab him with... oh fat Globalfine which is much cheaper, in this case we use Iati.
Payment card/currency exchange: we always go with Revolut definitely.
Roaming: NO There is, so if you have data enabled you can take a nice little gift back.
GPS: Maps.me Download the maps for Spain and they work great offline, whether you're on foot, by car, or on public transport.
Other destinations in California: 
