National Heritage Area Extension Act of 2005

National Heritage Area Extension Act of 2005 - Amends the Omnibus Parks and Public Lands Management Act of 1996 to: (1) extend to September 30, 2027, the authorization for making grants or providing assistance with respect to the National Coal Heritage Area, Tennessee Civil War Heritage Area, Augusta Canal National Heritage Area, Steel Industry American Heritage Area, Essex National Heritage Area, South Carolina National Heritage Corridor, America's Agricultural Partnership, Ohio & Erie Canal National Heritage Corridor (redesignated by this Act as the Ohio & Erie National Heritage Canalway), and Hudson River Valley National Heritage Area; and (2) increase the amount authorized to be appropriated for such areas.

Adds Lincoln County, West Virginia, and Paint Creek and Cabin Creek in Kanawha County, West Virginia, to the National Coal Heritage Area. Requires, with respect to such Area, the Secretary of the Interior to continue a certain contractual agreement with the National Coal Heritage Area Authority rather than the Governor of West Virginia.

Adds Berkeley County, South Carolina, to the South Carolina Heritage Area.

Reauthorizes appropriations for the New Jersey Coastal Heritage Trail Route. Directs the Secretary to prepare a strategic plan for the Route.

Adds six members to the John H. Chafee Blackstone River Valley National Heritage Corridor Commission. Requires the Commission to update the Corridor plan.

Mississippi River National Heritage Area Act - Establishes the Mississippi River National Heritage Area. Provides authorities and duties of the management entity for such Area, including development of an Area management plan.