Being a Brit I score quite highly on this:
Having only been to the states once and ignoring McD’s and Burger King, the best palce I’ve found to eat was Chilli’s in Ft Lauderdale, the staff were superb and the food was excellent. I particularly enjoyed the 2 for one offer on beer and the quantities of the shorts.
Never Eaten: #10 Dunkin’ Donuts
Never Seen: #15 Jack in the Box
Never Heard of: #32 Carl’s Jr.
What is the highest ranking chain that you’ve never eaten at (or otherwise visited)?
What is the highest ranking chain you’ve never seen in person (but may have heard of)?
What is the highest ranking chain you never even heard of?
#4 - Starbucks, although I have bought their products from the supermarket a time or two. After that is #10, Dunkin Donuts and #18 Outback Steakhouse.
#15 - Jack in the Box. Heard of it lots of times, but never seen one.
#31 - Popeye’s Louisiana Kitchen
As for the lowest, I think I ate at a Spaghetti Warehouse once. After that, the next lowest one I’ve heard of is #367 Taco Mayo, and the next lowest I’ve been to is #304 Gold Star Chili.
Looks like my grand total for places visited is 80.
Never eaten at Domino’s. Use to live about a quarter mile from one.
Chick fil A. None up here in the Great Northwest Wilderness.
Never heard of Texas Roadhouse.
What is the highest ranking chain that you’ve never eaten at (or otherwise visited)? Sonic, #13
What is the highest ranking chain you’ve never seen in person (but may have heard of)? I have heard of, but never seen, a Carl’s Jr., #32
What is the highest ranking chain you never even heard of? I don’t think I’ve ever heard of Zaxby’s, #58 - sounds vaguely familiar, but I’m not sure why. The highest I’ve definitely never heard of is Bojangles’ Famous Chicken 'n Biscuits, #67
Big Apple Bagels #397, once! It was good.
MaggieMoo’s Ice Cream & Treatery, #399, is the lowest I’ve heard of, but I’m not sure if I’ve ever seen one.
It’s funny these two answers are so low, because above these two, I really haven’t heard of most of them until you get closer to the top, and definitely haven’t been to them.
I’m also sort of surprised KFC is number 2. I see them around, but haven’t been in years, and they don’t seem to be as popular as some of the other top-ranked chains.
Geographical data: I am in NYC, reside in Queens, work in Manhattan, and visit all 5 boros and nearby suburbs all the time. In other words, pretty much at the center of the civilized world, so anything I am unaware of is completely unimportant 
Most of my fast food joint visits are emergency food stops on road trips, almost never as a planned meal, so even though I know of some of the top 25 (and maybe even know of a location near me) doesn’t mean I’ve ever hit them.
I see and hear ads for Sonic (#13) all the time but cannot recall ever seeing one. I visited their website and apparently they are drive-in only, and there is no space for drive-in restaurants in NYC! I found their online locator and there is only one within 30 miles of me, on a local route (Rte 17) in NJ that I do travel on a few times a year, but not on the stretch that I go on.
I have been to Arby’s (#14) and recall thinking their roast beef sandwiches were better than those at Roy Rogers, but it’s been 25 years since I’ve been in one. There are not many around. There is one not too far from me that I pass by from time to time, but other than that they’re pretty rare, so I’d have to intentionally set out to eat there.
There used to be a Jack In The Box (#15) near me that I passed by on a bus every day on the way to school. There was never more than 1 or 2 people in it, and my friend and I used to make fun of that fact as we went by. I never went there myself before it closed about 15 years ago, shortly after they took a hit in the news from some kind of E. Coli outbreak traced to their chain. Thus ends my awareness of JitB; I have not seen or heard commercials for them that registered with me. I didn’t know it was a national chain that still existed.
I am pretty sure I’ve had Domino’s Pizza (#9) but not by my own volition for 30+ years, and I wouldn’t call them a “chain restaurant” as nobody visits one and sits down to eat there, they’re delivery only AFAIK, right?
Rounding out the Top 25, I have never been to a Dairy Queen (#21) or a Denny’s (#24), though I have seen them while driving around the Northeast somewhere. There doesn’t appear to be a DQ in NYC or Long Island, though there are quite a few in Northern NJ. There are only 2 Denny’s found near me, both in parts of NJ I don’t often visit other than by passing through on the NJ Turnpike (near Rahway and in East Brunswick).
I know I’ve seen Panera Bread but mostly in the ring of suburbs around Baltimore, where I lived for 2 years or so. There’s apparently one very close to me that I must have noticed at least subconsciously, but have never visited.
Sonic
Chick-fil-A
Chick-fil-A
1 - Panera; the wife will go, however.
2 - Panda Express
3 - Zaxby’s
FWIW, ain’t a one of them on the list within 15 miles of my house. The winner, at 16 miles, is Bojangles.
Until very recently I’d never heard of #67, O’Charley’s, but there is a new one pretty near me and they are jammed to the rafters every night.
Road Trip!
On review, I see I didn’t quite answer the questions posed in the OP, so will do so now.
Lowest-ranking chain I’ve actually eaten at is #360 Ground Round.
Count me amongst the others who are purplexed over the high ranking for #58 Zaxby’s. I’ve been all over the country and never noticed one of these. What do they serve? Do they go by some other trade name?
Sonic (#13). Technically you could say I haven’t intentionally eaten at Domino’s…my one experience with them was a single slice of pizza that I thought came from a local place and only found out later was from Domino’s.
Whataburger (#41). I hear about it all the time…never actually seen one.
Zaxby’s (#58). Include me in the “huh?” category for this one. It’s based in Athens, GA but despite an extended trip to the metro Atlanta area a few years ago I still cannot recall that name.
Lowest seen: MaggieMoo’s (#399)
Lowest eaten: Hot Dog on a Stick (#388)…mmmm, cheese on a stick and a lemonade.
Moving thread from IMHO to Cafe Society.
Ah, this is an interesting question not in the OP but a natural extension.
I’ve eaten at #390, SushiSamba, which indeed is only in NYC. It has all of EIGHT locations, so I don’t see how they’re a “chain”? (I also only know of 2 locations, they must be doing pretty well.) They’re pretty expensive places too, and for full service sit-down meals with reservations typically required.
Up from that though, I have to roll on up to #308, ESPNZone, for an establishment I’ve personally walked into. I’ve been to the one in Baltimore’s Inner Harbor and another one somewhere else, though not the one in Times Square. Past that and it’s all the way to #250, Smith and Wollensky, a top quality steakhouse at its original location on Third Ave and 49th St. in Manhattan and which I didn’t even know existed as a “chain”.
Other than #254 (Haagen-Dazs Ice Cream), most of the “Bottom 250” are complete unknowns to me even by name. I’ve heard of #399, “MaggieMoo” - there is one near me but I haven’t been to it. Similarly #312, “Fatburger”, as a California burger joint that from time to time is mentioned as a standard of fast food burger used to pity us Easterners who’ve never had it (along with “In-N-Out”)
And #270, “Quaker Steak and Lube”? Seriously?!!
Scrolling down through the list, it’s fair to say that only 1/3 to 1/2 of the entries are places I know about or spent money in. And there are quite a few gas stations (!) in the mix…
Never eaten at: #4 - Starbucks – That’s a restaurant? I thought it was just a coffee place…
Never seen: #32 - Carl’s Jr
Never heard of: #58 - Zaxby’s
Lowest I’ve eaten at: #360 Ground Round Grill & Bar – There used to be a Ground Round a few miles from home. I loved it, because they never, ever, ever carded. I don’t know how they stayed in business as long as they did, because the place was always filled with drunk 17-year-olds.
Lowest I’ve heard of: #398 Good Times Burgers & Frozen Custard – Never been, but there’s one very close to my brother’s place in Colorado. He’s mentioned going there a couple of times.
Local bonus: Hey, Jersey Mike’s is on the list! Way to go guys…in the top 200, even.
For what it’s worth, there’s a SushiSamba in Chicago. Something tells me there might be one in Vegas, but I’m not certain of that.
Lowest I’ve eaten at? #400: The Spaghetti Warehouse.
In the beginning I was certain I’d get around 300 of them but after the first 70 or so I was lucky to get over 100 in the end barely.