The border crossings are in transition to require everyone entering the US to have a passporet, regardless of means of travel. Currently, if you are flying into the US, you must have a valid passport and, depending on your country of origin, you may also need a visa.
The deadline for driving across the border was pushed back, but may be in effect by the time GateCon rolls around. I renewed my passport this year in January when I was planning my Scotland trip. I got the completed and renewed passport before the city courthouse cashed my check to pay the processing fee.

The Feds have hired a lot more people to process passports and it takes a lot less time. Because it is so close to the event, you can also pay the expidition fee for faster processing.
This question came up somewhere else (not MOL) about clearing Customs and getting the finger print scan. It goes really fast. The little finger scanner gadget scans both hands at once. If you are entering the US, have your passport ready and your Customs form filled out beforehand. Be polite and follow directions and you shouldn't have a problem. The Customs inspectors can sometimes be buttheads, but you don't want to argue with them or you may find the entry process a lot longer.
I had no problems re-entering the US after spending nearly 2 weeks in Scotland. I had to go through an additional clearing since I stayed on at a B&B that was on a farm, but it went really fast. Just don't bring in any agricultural products or animal products and you'll be fine.
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