I did the first, obvious query: [ seedless grapes ]
I read the Wikipedia article which tells me that sultanas--also known as Thompson seedless--are probably the most common (widely grown) kind of seedless grape. (This gets a little complicated because the word "sultana" really refers to a kind of Turkish grape, AND is the common name for "raisin" in much of Europe.) But after poking around a bit, it's pretty clear that while seedless grapes have been around intermittently (as mutant variants that didn't breed true), the Thompson seedless is the dominant kind of seedless grape.
So, let's look up [ Thompson seedless ]
I'm hoping to find some nice general articles about this variety of grape, maybe with some background.
The first hit is an interesting, if somewhat technical article from the University of California Cooperative Extension. It's useful (if you raise Thompson seedless grapes in volume), but not useful for our purpose--there's no history here.
The other articles on the SERP are similar--interesting, but not useful to us.
How about the query: [ Thompson seedless history ] ? Here, the first hit is from Raisins.org (which turns out to be a page from the Raisin Administrative Committee in Fresno, CA, not far from where I saw all the grapes).
On this page they mention that William Thompson (an immigrant from Scotland) introduced the Lady deCoverly seedless grape. Interesting. Should we believe the story? Maybe. They're located in Fresno and have historical ties to the grape industry, so it makes sense that they'd know.
But let's dig deeper and triangulate this bit of information.
The 3rd result on this page is a link to the "Historical Marker Database," a record of roadside history markers. (Interesting source--not necessarily a source of grape history expertise, but let's read what they say.)
"Thompson... in 1872 sent to New York for three cuttings called Lady deCoverly of which only one survived."
Even better, they claim that the first Thompson grape was grown on his farm near the site of the marker:
the raisins were squeezed between two grooved rubber and toothed-metal rollers, which exposed the seeds. The seeds were then forced out a chute at the front (pushed out by the metal-toothed rollers) and the raisins dropped below the rollers
Remember that our task for this challenge is to: