The answer depends on where you are coming from. If you are a United States citizen, located in the US, and will not be transiting through a foreign country (an example is driving from Alaska, through Canada, to the lower 48 states) then you will not need a passport.
In the Alaska example, flying from Alaska direct to a point in the "lower 48" will not require a passport.
If you are a citizen of Another Country, the answer is likely "yes", and could require you to have an American visa if your stay is over 90 days in country. Go to http://travel.state.gov/visa/visa_1750.html for more information.
Yes, you do need your passport.
does my passport need to be in date to go to belfast
Do you need a passport to travel to Barcelona
Yes you do have to have a passport to go to Chile.
You need a passport to go anywhere.
You need a passport to go anywhere out of the country!
Yes, you need a passport to go to the Bahamas.
Yes, you do. A passport and a visa.
Yes, you do. Anytime you go into another country, you need a passport.
Branchwood Subdivision: lots of houses for the amount of walking.
Yes, you do need a Visa to go to Mozambique with a Thai passport. Regardless of the passport country of origin, you will need a Visa to visit if you are not a native of Mozambique.
Yes, you definitely need a passport to go to Honduras on a cruise ship. More particularly, you will need a passport to re-enter the United States.