As part of its mission, the Delphi Preservation Society has prepared and/or supported applications nominating Carroll County districts and structures to the National Register of Historic Places. Those include:

• The Delphi City Hall and Opera House (1998)

• Wilson’s Bridge over Deer Creek on County Road 300N (2001)

• Deer Creek Valley Rural Historic District along Deer Creek (2002)
  It was the second district in Indiana to achieve this status.

• The Carroll County Courthouse (2003)

• Delphi Courthouse Square Historic District (2010) including 43 buildings in the blocks immediately surrounding the square.

• The Delphi Methodist Episcopal Church (2015)

• The South Delphi Historic District (2024)

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In 2015, the Society published the brochure Carroll County Sites and Structures in the National Register of Historic Places and the State of Indiana Register made possible by an Historic Preservation Education Grant from Indiana Landmarks, Indiana Humanities, and the National Endowment for The Humanities.