Why does North Dakota have its own bank?

BANCO DO BRASIL AMERS 18 Bank of Landisburg 7 California Pacific Bank 4 Citizens Bank of Kansas 5 Citizens Bank of Morgantown 1 First Bank of Owasso 3 First National Bank in Tigerton 3 First National Bank of Raymond 1 First State Bank of Brownsboro 9 GERMAN AMER Bank 16 Legence Bank 9 Method Bank 10 Minnesota National Bank 10 OLD National Association National Bank 11 Park Bank 3 Security Trust & Savings Bank 7 Thayer County Bank 2 TrailWest Bank 4 VANTAGE Bank TX 11 WATERFORD Bank National Association 5