Colorado - Criteria: C (architecture/engineering)
| 19th Street Bridge |
| 7-D School |
| Adams County Courthouse |
| Adobe Stables, Arkansas Valley Fairgrounds |
| Akron Gymnasium |
| Alamo Placita Park |
| Alamosa County Courthouse |
| Alamosa Post Office |
| Alexander House |
| Alger, Amanda K., Memorial Methodist Episcopal Church |
| All Saints Church of Eben Ezer |
| All Saints Episcopal Church |
| Alpine Hose Company No. 2 |
| Alpine Tunnel Historic District |
| Altamaha Apartments |
| American Legion Hall |
| American National Bank Building |
| Ammunition Igloo |
| Anderson Barn |
| Anderson, Peter, House |
| Animas Forks |
| Annunciation Church |
| Ansel Hall Ruin |
| Antlers Cafe and Bar |
| Arapahoe Acres |
| Arapaho Hills |
| Armstrong Hotel |
| Arnett-Fullen House |
| Arno Apartments |
| Arrowhead Lodge |
| Art Building |
| Arvada Downtown |
| Arvada Flour Mill |
| Aspen Community Church |
| Astor House Hotel |
| Atchison, Topeka and Santa Fe Passenger Depot |
| Atwater, Samuel H., House |
| Aultman House |
| Auraria 9th Street Historic District |
| Austin Building |
| Avery House |
| Avoca Lodge |
| Baca House and Outbuilding |
| Bailey House |
| Bain Cabin |
| Baker House |
| Baldpate Inn |
| Bancroft, Caroline, House |
| Barker, Hannah, House |
| Barker House |
| Barndollar-Gann House |
| Barnes-Peery House |
| Bastien's Restaurant |
| Battlement Mesa Schoolhouse |
| Bauer Bank Block |
| Baxter House |
| Bear Creek Canyon Scenic Mountain Drive |
| Bear Lake Comfort Station |
| Beaumont, Allen, J., House |
| Beaumont Hotel |
| Beckwith Ranch |
| Bee Farm |
| Bell and Canant Mercantile-Crossan's M and A Market |
| Bell Mercantile |
| Bemis Hall |
| Bemis, Judson Moss, House |
| Benevolent and Protective Order of Elks Lodge |
| Bennett-Field House |
| Benson, A.S., House |
| Bent County Courthouse and Jail |
| Bent County High School |
| Bergen Park |
| Big Thompson River Bridge III |
| Big Thompson River Bridge IV |
| Bimson Blacksmith Shop |
| Black, Dr. John A., House Complex |
| Black Forest School |
| Black Squirrel Creek Bridge |
| Bloom, Frank G., House |
| Bluebird Theater |
| Boat Tow |
| Bode-Stewart House |
| Boggs Lumber and Hardware Building |
| Boggsville |
| Bonney, J. M., House |
| Borland, Maude Stanfield Harter, House |
| Boston Building |
| Botanical and Horticultural Laboratory |
| Boulder County Poor Farm |
| Boulder Creek Bridge |
| Boulder Crescent Place Historic District |
| Boulder Valley Grange No. 131 |
| Bouton, Jay H., House |
| Bouvier-Lothrop House |
| Bowen Mansion |
| Bowles-Cooley House |
| Bowles House |
| Bowman, William Norman, House-Yamecila |
| Brannan Sand and Gravel Pit #8-Lake Sangraco Boathouse Complex |
| Briarhurst |
Data from United States Park Service and Wikidata
