The U.S. Coastal states are states in the United States that have a coastline. This can be an ocean coast, a gulf coast, or a Great Lake coast (all of these are covered by the U'S' coast guard). Let's count the states, coast by coast.

There are 14 Atlantic Ocean states: Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut, New Jersey, New York, Delaware, Maryland, Virginia, North Carolina, South Carolina, Georgia, Florida.

There are 5 Pacific Ocean states: California, Oregon, Washington, Alaska, Hawaii.

There are 5 Gulf of Mexico states: Florida, Alabama, Mississippi, Louisiana, Texas.

There is 1 Arctic Ocean state: Alaska.

Add those numbers up and you seem to have 25. But that's not the right answer because we've counted Florida twice (both an Atlantic Ocean state and a Gulf of Mexico state) and we've counted Alaska twice (both a Pacific Ocean and Arctic Ocean state). So "22" is obviously not the right answer since it is one short of our current total 23. We also need to count the states that have a coastline on the Great Lakes.

There are 8 Great Lakes states: New York, Pennsylvania, Ohio, Indiana, Illinois, Michigan, Wisconsin, Minnesota.

Add those to the current total of 23 and don't we get 31? No, because New York was counted twice (both an Atlantic Ocean state and a Great Lakes state). So the answer is indeed 30.

More Info: en.wikipedia.org