They are found in most areas of North America, so finding them in non-desert, non-mountainous areas should be relatively easy. There are multiple varieties. If you look around, there are probably some growing nearby. They are easy to identify, as no other plant produces that brown seed head that all cattails do. There are similar looking plants that can grow in close proximity, but none have that seed head. As a word of caution though, if you are not sure then don't eat it. Some of the broad leafed grasses that grow on the edges of ponds are poisonous.