- Wartime 21
- Urban Planning and Design 35
- Transportation 39
- Technology 13
- Suburbs 79
- Sports 26
- Sexuality and Gender 9
- Science 6
- Rock and Roll 10
- Religion 88
- Recreation 26
- Race and Ethnicity 125
- Public Housing 4
- Public Art 12
- Protest 5
- Parks 42
- Neighborhoods and Districts 66
- Music 25
- Museums 37
- Libraries 18
- Labor 14
- Inventors 7
- Industry 67
- Immigration 67
- Healthcare 25
- Great Depression 11
- Government and Politics 33
- Food 42
- Events 26
- Environment 58
- Entrepreneurs 31
- Entertainment 74
- Education 71
- Economy 6
- Early Settlers & Settlement 27
- Disasters 9
- Crime 15
- Conflict 25
- Civic Organizations 65
- Cemeteries 17
- Businesses 67
- Bridges 13
- Biography 78
- Aviation 7
- Art and Design 25
- Architecture 174
- Agriculture 18