Exhibit 21-A

OTTER TAIL CORPORATION

Subsidiaries of the Registrant

February 25, 2011

Company	State of Organization
Otter Tail Power Company		Minnesota
Otter Tail Energy Services Company, Inc.		Minnesota
Overland Mechanical Services, Inc.		Minnesota
Green Hills Energy, LLC		Minnesota
Sheridan Ridge I, LLC		Minnesota
Sheridan Ridge II, LLC		Minnesota
Otter Tail Assurance Limited		Cayman Islands
Varistar Corporation		Minnesota
Northern Pipe Products, Inc.		North Dakota
Vinyltech Corporation		Arizona
T.O. Plastics, Inc.		Minnesota
DMI Industries, Inc.		North Dakota
DMI Canada, Inc.		Ontario, Canada
DMI Equipment, LLC*		Delaware
BTD Manufacturing, Inc.		Minnesota
Miller Welding & Iron Works, Inc.		Minnesota
ShoreMaster, Inc.		Minnesota
Galva Foam Marine Industries, Inc.		Missouri
Shoreline Industries, Inc.		Minnesota
Aviva Sports, Inc.		Minnesota
ShoreMaster Costa Rica, Limitada		Costa Rica
DMS Health Technologies, Inc.		North Dakota
DMS Imaging, Inc.		North Dakota
DMS Health Technologies – Canada, Inc.		North Dakota
DMS Topline Medical, Inc.		North Dakota
Aevenia, Inc.		Minnesota
Moorhead Electric, Inc.		Minnesota
Foley Company		Missouri
E. W. Wylie Corporation		North Dakota
Idaho Pacific Holdings, Inc.		Delaware
Idaho-Pacific Corporation		Idaho
Idaho-Pacific Colorado Corporation		Delaware
AWI Acquisition Company Limited		Prince Edward Island, Canada
AgraWest Investments Limited		Prince Edward Island, Canada

*Inactive