Sinkholes form when water erodes the supporting bedrock away. They are more common in areas where carbonates, including dolomite and gypsum, formed as water evaporated to create bedrock.
Carbonates are highly soluble in acidic aqueous solutions, including acid rain. Acid rain causes channels to form within the bedrock and subsequent rainfall continues the erosion process. As channels grow larger, some combine until the underlying structure collapses. Without the support of bedrock, the upper layers of soil collapse into the hole, forming the sinkhole.
One area that sinkholes are common is Florida, because of the abundance of marshlands and frequent rains. However, sinkholes do form in many areas across the United States.