California Olive Ranch is good. They grow and sell their own, and repackage imported oil. Their local stuff is very good quality. They have some single varietals (as opposed to blends) that are very tasty.
Yup, I second this. It's pretty much the only widely available high-quality affordable brand in the US. You tend to see chefs on cooking shows use it as their basic everyday olive oil.
There are plenty of great niche/imported brands as well, but it's pretty random as to which store might carry which ones, if any.
How can you reliably differentiate their local stuff from the oil that's mixed with imported oil, or even know whether the imported oil is EVOO?
IIRC they're no longer certified by the COOC. Given the massive amount of fraud in the olive oil industry, independent verification seems like the only tool to do that.
But even if you want to go by the seat of your pants, it seems like a bad idea to trust a company named "California Olive Ranch" whose growth into a nationally known label depends on importing olive oil from outside California.
Easy. I only — and I know this sounds silly — drink domestic :) I actively avoid imported olive oil for just the reasons you suggest. Last I looked, something like 50% of oil labelled “Italian EVOO” was in fact not, and a solid proportion of it wasn’t even olives. I’m not gambling with that, especially getting it shipped internationally.
California grows olives just fine, so I always use California oil. Now, is California Olive Ranch cheating some cheap import oil into their native EVOO? They could be; I’m betting not. My bet is that their own interests are best served by being straight here — one credible allegation of adulterating oil and their reputation takes a huge hit. Meanwhile, they can continue to charge lots of money for a high-quality product, which is just as it should be.
There are plenty of great niche/imported brands as well, but it's pretty random as to which store might carry which ones, if any.