In my research, I was impressed that some communities do apparently pay attention to statistics. I infer this from their statement that they formerly held the title of such-and-such, thereby implying some other town has beaten them out. Also, I found instances where some private web site—one belonging to a vacation resort, for example—claimed that their community held the title of "Something-or-other Capital of the World," but when I checked the official website of the town, I found the actual claim was something more modest, such as "...Capital of the Midwest."

Here's my list for Minnesota:

[For each town, the first link goes to a Wikipedia article, which sometimes reports the claim—and the second goes to the town's own official web site or to some other organization that makes the claim.]

Anoka, Minnesota – Halloween Capital of the World

Askov, Minnesota – Former title: Rutabaga Capital of the World (Forest Grove, OR and Cumberland, WI now claim it) Askov acknowledges that their title lapsed when the rutabaga warehouse burned down!

Austin, Minnesota – Spamtown, USA, a.k.a. Spam Capital of the World. (They're referring to the canned meat, not the junk email.)

Baudette, Minnesota – Walleye Capital of the World – Port Clinton, OH also claims the title.

Braham, Minnesota – Homemade Pie Capital of Minnesota. They cite the state legislature as their authority.

Clontarf, Minnesota – Former title: Hay Capital of the World – now claimed by Inola, OK and Gilbert, AZ.

Cloquet, Minnesota – Former title: White Pine Capital of the World – now claimed by Marinette, WI.

Dorset, Minnesota – Restaurant Capital of the World. I assume they base their claim on the number of restaurants per capita since it is a very tiny town.

Ely, Minnesota – Canoe Capital of the World

Ely, Minnesota – Sled Dog Capital of the World – They've never heard of Alaska, apparently.

Fountain, Minnesota – Sinkhole Capital of the World – also claimed by Palmyra, PA. They're referring to the geological phenomenon.

Hibbing, Minnesota – Former title: Iron Capital of the World – "Iron Capital of America" is claimed by Warren, MI.

Hopkins, Minnesota – Raspberry Capital of the World

Lake Benton, Minnesota – "Original" Wind Power Capital of the Midwest. I assume the "original" means it has been surpassed.

Lanesboro, Minnesota – "thought of by many as" Amish Capital of the World. Those "many" have never visited Ohio or Indiana, apparently.

Lanesboro, Minnesota – Rhubarb Capital of Minnesota – more defensible than "Amish capital".

Longville, Minnesota – Turtle Racing Capital of the World

Madison, Minnesota – Lutefisk Capital USA. The world capital would have to be in Norway, I suppose.

Minneapolis, Minnesota – Former title: Flour Milling Capital of the World (I think all the mills are closed now.)

Montgomery, Minnesota - Kolacky Capital of the World

Moose Lake, Minnesota – Agate Capital of the World

Mountain Iron, Minnesota – Taconite Capital of the World

Olivia, Minnesota – Corn Capital of the World

Pine Island, Minnesota – Former title: Cheese Capital of the World. Have they never heard of Wisconsin?

Preston, Minnesota – Minnesota's Trout Capital

Taylors Falls, Minnesota – Pothole Capital of the World. They're referring to the natural geological formation, not the breakdown of pavement.

Winona, Minnesota – Stained Glass Capital of the United States

Worthington, Minnesota – Turkey Capital of the World - Actually, Worthington has an annual competition with Cuero, TX for the right to call itself Turkey Capital of the World—the winner is decided by a turkey race!

Some web sites I ran across in my search:

http://www.offices.net/city-slogans.htm

http://www.epodunk.com/slogans/

http://en.wikipedia.org/wiki/List_of_city_nicknames_in_the_United_States

http://www.usacitiesonline.com/mottos.htm

http://american-worldcapitals.blogspot.com/