Are those inspection stations at the Arizona and California borders still in use? Are they used only for agricultural products? Was there ever one at the California/Nevada or California/Oregon borders?
The stations are still there, and exist on the CA/NV border. You may not find them operating, however. Although, this letter to the editor, dated quite recently, implies that the station at Truckee is operating:
These are the little places that take away your little cactus plants that you dug up from the desert and were intending on planting in a flowerpot back home?
They were operating in Truckee when I went up to ski in Tahoe back in February.
Yep, still there. They usually just wave passenger vehicles through.
As far as I know they’re only concerned with agriculture. They don’t want pests going to places like Napa.
The one on the 10 between Phoenix and LA is always open.
I don’t know if it’s always open but there’s also an inspection station just east of Needles on I-40, a bit west of the CA/AZ border.
The one outside Barstow (Yermo) on the 15 is always open. They usually don’t stop regular cars, unless they look shifty. But they check trucks. It’s a regular bottleneck coming home from Las Vegas.
Haven’t been through there in a couple of years, but the last time I was it was closed.
That’s probably the reason.
Most of the Ag stations were closed due to budgetary issues and were later reopened once the tax revenues came back. I wonder what’ll happen now considering the shortfall California’s currently facing.
Here’s the CA website blurb on the stations, which list 16 of them, and has a link to a map (PDF). Although the text appears not to have been updated since 2000:
http://www.cdfa.ca.gov/phpps/pe/Exterior.html
The map is dated 2005, and the locations along the AZ, NV and OR borders are probably accurate.
Not to hijack my own thread, but are there still the INS random checkpoints along the freeways?
No, I"m not going to smuggle illegal immigrants or agricultural products. I’ve been spending a lot of time on West Coast Roads. This website is addicting to a geography nut like myself.
I don’t know about the Western states, but either the INS or the DEA ran checkpoints in South Florida on cars coming from Key West looking for drugs/illegal immigrants during the 80s. This led to Key West seceding from the Union and several minutes of civil war.
The Truckee station was staffed last weekend when I went through. However, I was waved through, presumably because I had CA plates and wasn’t driving a commercial truck. I wasn’t paying enough attention to see if anyone was being stopped and quizzed or searched, but a couple years ago, I recall cars were being split into two lanes: cars with CA plates and cars with other states’ plates. The CA plate lane was just a smile and a wave, but the other states’ lane was stopping everyone.
A few years ago, I was coming back into CA from Arizona, probably either at Needles or Vidal, and the agent asked where I was coming from and was relieved to hear that I’d only been as far into AZ as Yuma. I gathered that vehicles that had been to other parts of AZ or Nevada were getting a full hands-on search that day.
Years ago in CA we always called them “the bug stations.”
Well, it’s hardly random, but there is still the huge INS/CHP/USDA checkpoint on the 15 just south of Temecula.
With Nevada plates I only once was stopped (we had a banana on the dashboard and the officer at the Truckee checkpoint acted like it was plutonium… and confiscated it).
I was once stopped there behind an older couple with a giant Buick or similar with British Columbia plates. They had to open the trunk and both get out of the car. I wanted to tell the officer they were from Canada, not Colombia. 
My first experience with them, I had a grapefruit in the car, I believe at the Truckee station, with CO plates on the car. By the time I reached the officer, I was holding it out the window. He barely glanced at it, and said “Is that Arizona grapefruit all you have?”. I said “yeah” and he waved me through. I wondered how they distinguished the provenance of a grapefruit from a distance of 10 feet.
The inspection station on the coastal California-Oregon border (Highway 101) is still open and manned, although I don’t know if they ever stop anyone any more: my parents have local Oregon plates, and just get waved through. Ten years ago or so, though, we used to have to throw out fruit and such at the checkpoint, if we had any.
There’s also one on Highway 50 in South Lake Tahoe. It seems to be open about half the times I pass it, but seemingly never stops passenger cars. In the 30-odd years that I can remember traveling in the Tahoe area (which we do several times a year), I can remember being stopped once, and that was probably 25 years ago.