Iowa - Criteria: A (event)
| Coggon Public School |
| Colfax Spring City Commercial Historic District |
| College Corner Commercial Historic Business District |
| College Hall |
| College Square Historic District |
| Collegiate Neighborhood Historic District |
| Collins-Bond House |
| Colonials Club House |
| Columbus Junction School 1882-1920 |
| Commercial Hotel |
| Community Building |
| Conant's Cabin and Park |
| Concord Congregational Cemetery |
| Conover, Thomas J., House |
| Cook, Clarissa, Home for the Friendless |
| Cook-Johnson House |
| Coralville Union Ecclesiastical Church |
| Corbett's-Eby's Mill Bridge |
| Corning Commercial Historic District |
| Corning Opera House |
| Cottage Grove Avenue Presbyterian Church |
| Council Bluffs Free Public Library |
| Court Hill Historic District |
| Courthouse Square Historic District |
| Crapo Park and Arboretum Historic District |
| Craven, J. D., Women's Relief Corps Hall |
| Crescent Warehouse Historic District |
| Cresco Opera House |
| Cretsinger, John, House |
| C.S.P.S. Hall |
| Cundill Block |
| Czecho Slovakian Association Hall |
| Dahlonega School #1 |
| Dallas County Courthouse |
| Danish Lutheran Church |
| Davenport City Hall |
| Davenport Crematorium |
| Davenport Hotel |
| Davenport Motor Row and Industrial Historic District |
| Davenport Village |
| Davenport Water Co. Pumping Station No. 2 |
| Davis County Courthouse |
| Decorah Commercial Historic District |
| Decorah Ice Cave |
| Decorah Municipal Bathhouse and Swimming Pool |
| Decorah Woolen Mill |
| Delmar Calaboose |
| Delta Upsilon Chapter House |
| Democrat Building |
| Denmark Congregational Church |
| Denny, Professor Charles O., House |
| Des Moines County Court House |
| Des Moines Fire Department Headquarters-Fire Station No. 1 and Shop Building |
| Des Moines River Locks No. 5 and No. 7 |
| Des Moines Western Railway Freight House |
| Diamond Jo Boat Store and Office |
| Dibble House |
| Dobbin Round Barn |
| Dodd, A. B. C., House |
| Donahue Building |
| Douglas, George B., House |
| Downey Savings Bank |
| Downtown Commercial Historic District |
| Downtown Commercial Historic District |
| Dows Street Historic District |
| Dowtown Perry Historic District |
| Drake, John and Amanda Bigler, House |
| Drake Public Library |
| Drake University Campus Historic District |
| Dr. Salsbury's Laboratories, Main Office and Production Laboratory Building |
| Dubuque Casket Company |
| Dubuque City Hall |
| Dubuque County Jail |
| Dubuque Freight House |
| Dubuque, Julien, Monument |
| Dubuque Millworking Historic District |
| Dubuque Star Brewery |
| Dubuque YMCA Building |
| Dugan's Saloon |
| Duncan-Duitsman Farm Historic District |
| Duncan, John M., House |
| Dunham, Z. T., Pioneer Stock Farm |
| Dyas Hexagonal Barn |
| Eagle Point Park Historic District |
| Earlham Public School |
| Early, John and Elizabeth McMurn, House |
| East Amsterdam School |
| East Des Moines Industrial Historic District |
| East Park Band Shell |
| East Park Historic District |
| Eckle Round Barn |
| Economy Advertising Company |
| Edel, Matthew, Blacksmith Shop and House |
| Edgewood School of Domestic Arts |
| Edmundson Park Historic District |
| Eldon Carnegie Public Library |
| Eldora Downtown Historic District |
| Elgin Block, The |
| Elkader Downtown Historic District |
| Elkader Opera House |
Data from United States Park Service and Wikidata
