- 1 Civil service reform
- 344 Civil War, 1861-1865
- 2 Civil wars
- 2 Claghorn, James Lawrence, 1814-1889
- 2 Clapboard siding
- 1 Clapp & Greenwood's Factory
- 1 Clare, of Assisi, Saint, 1194-1253
- 4 Clarinets
- 1 Clark & Son's Painting
- 1 Clark and Beatty (Hosiery)
- 2 Clark Park
- 2 Clark Thread Co.
- 7 Clark, C.H. Lumber Yard
- 1 Clarke, Campbell
- 1 Clarke, Charles Cowden, 1787-1877
- 2 Clarke, John Gold Leaf Factory
- 1 Clarke, Mary Cowden, 1809-1898
- 1 Clarrisa Harlowe
- 2 Clasps (fasteners)
- 4 Classical Institute
- 1 Classical Institute
- 7 Classical Revival (European revival style)
- 3 Classrooms
- 1 Clavichords
- 3 Claxton, Remsen & Haffelfinger
- 2 Clay, Cosack & Co.
- 3 Clay, Henry, 1777-1852
- 3 Cleaners
- 7 Cleaning
- 1 Clearfield Chemical Works-William Adamson
- 3 Clearfield County, Pennsylvania
- 8 Clearfield Street
- 1 Clearfield Textile Machine Co.
- 1 Clearview Street
- 1 Cleavers (culinary tools)
- 1 Clein, Francis, 1582-1658, active in England
- 9 Clemens, Samuel Langhorne, 1835-1910
- 3 Clement I, Pope
- 2 Clement, E. School
- 2 Clement, William James, 1802-1870
