Where to Start When You Need a Passport

The United States recognizes 192 countries. Suffice it to say, each country has its own rules and regulations for entry. The U.S. Department of State is the official source for passport and visa requirements. Contact information is available online at the U.S. National Passport Information Center, including a help line at (877) 4USA-PPT. The agency suggests you allow 4-6 weeks for passport processing. If you need to travel unexpectedly and require a passport sooner, visit How to Get Your Passport in a Hurry.
The following links will see you from start to finish:
New Travel Rules for Western Hemisphere Travel Initiative (WHTI)
U.S. State Department's Travel and Business Information Page