it really depends on what you are trying to get into as every state/region/city offers something different. if you want history...boston, nyc, philly, dc offer the most. the west coast is a different country compared to the east coast. same with the south. and if you did not know, to fly coast to coast takes 5-6 hours depending on where you start/finish.

chicago is a great city. same with san francisco. san diego is amazing in terms of relaxing.

so my recommendation is to determine what you want to get into...and go from there. you have your major cities, your secondary cities, and then your niche markets. each has something to offer the other does not.

I'm for Chicago too. I'd aim for a hotel somewhere convenient for the Loop. The Palmer House is quirky, historic, reasonably priced and has great public transport connections.

Early September means Labor Day and could affect hotel prices. That said, I spent 2016 Labor Day at the Palmer House and it was a real bargain.

For 4 days, yes, just keep it to one city.

Boston
New York
Washington
Orlando
San Francisco

Those will have plenty of things to do.

I don't know if anyone answered you on NYC airports, but Newark and JFK both work for international flights. I wouldn't favor one over the other, YMMV.

Depending on your days I'd look at LHR-EWR/JFK. I give a slight edge to EWR for arrival as less flights arriving into Terminal B during the day. And JFK-LCY if you're looking for new experience. The 2x2 all J class A318 is unique for BA CW and a nice arrivals experience in downtown London if that is your final destination or connecting to one of the few BA serviced cities from LCY.

This is doable and great, but you will be doing a ton of driving. I live in Washington DC. In December, I flew from DC to LAS and hiked 17 miles in the Grand Canyon for a weekend.

I flew from DC to LAS Friday after work. Met a friend in Vegas and we stayed in hotel overnight. Got up early and drove from 4 am - 8 am to Grand Canyon (we were jetlagged on East Coast time so our bodies thought it 6:00 when we started driving). We hiked the 7.5 mile South Kaibab Trail to the bottom of the canyon and camped overnight. Hiked the 9.5 mile Bright Angel Trail the next day (Sunday). Then we drove to Vegas, showered, and took our flights home.

Unfortunately, Spirit Airlines is the only airline with a redeye flight from LAS to the DC area, and I needed a redeye flight in order to do all of that in a weekend. American was cheaper but I would have needed to connect in Chicago at 4 in the morning (Plus connecting in Chicago in the winter is always risky due to snow storms). So I took Spirit even though is was more expensive..

As for NYC airports, JFK and EWR are the main international airports (LGA is more short-haul flights). I personally find JFK and EWR to be pretty equal in terms of ease and time getting to Manhattan.

Dubuque, Iowa

Florida, Best place to visit. :)

Not in September; when it is still hurricane season, intensely humid and rain is very likely. I live there and the best thing about September is knowing that July and August have passed. I'm not sure of a good four-day destination in Florida which doesn't require a fair drive from the airports (perhaps St Augustine) or insane ticket prices (Walt Disney World).

Most importantly, don't waste that Companion Ticket deal in Economy. By the time you pay your surcharges and taxes; you'll have saved very little but lost a lot of choice. Good luck with your final selection. I'd say to maybe try Seattle but that's a long flight for a four-day trip. I'll be heading to Chicago for four days on Labor Day weekend again. So much to do and no car needed; great eating and entertainment; beautiful parks and lakeside (with beaches); river trips; Adler Planetarium, Shedd Aquarium, Field Museum, Navy Pier and (best of all) Wrigley Field. I'd rather pay for Cubs tix than Disney tix. Go back to the UK and tell the folks that you saw the MLB World Champs (at last).

If you're interested in LAS and the grand canyon, check whether there are flights to LAX, then buy a cheap flight to LAS from there. Several airlines offer the flight for around $100 (that's in economy, but it's only 1 hour). You could even stay one night around LAX to see the Hollywood sights. Or you could do the same thing at SFO which also has cheap flights to Vegas.

Thirded. Second would be LAS and last on my list would be anywhere in Florida...unbearable humidity!

For four days? Don't get me wrong, I love San Diego, I was there at Christmas and will be there again at Easter but, it's a helluva long way even in Club.

4 days (minus the time to get there from LAS) at Grand Canyon seems too short to me. Grand Canyon Village is quite a bit of driving away from LAS and it probably takes you more than 3 days to fully see that part of the Grand Canyon.

No. Especially not in September. :)

For four days in Sept from the UK I'd stick with the east coast, and probably just one city. Four days is enough for an overview of NYC. It's a good amount of time for Washington DC (how much time do you really want to spend in museums and taking photos in front of the White House?). It's also a good amount of time for Boston.

Or, if you want to see more of the South, Charleston SC and/or Savannah GA are nice for a few days. If you just want a tourist experience go to Orlando and spend a few days at the theme parks. I know it's hurricane season, but that doesn't mean there will be a hurricane there.

The missus recommended Boston too. I've not been but heard only good things.

It's big enough that they have good mass transit and restaurants and the like, but small enough to be manageable. Lots of US colonial history and interesting walking tours - that kind of thing. Good shopping and restaurants too.