| 1931 EARNEST Railroad Crossing Gate Patent Print |
| 1931 MUELLER Automatic Hydraulic Crossing Signal |
| 1931 SORENSEN Highway Crossing Signal Patent |
| 1931 FERGUSON Railroad Crossing Gate Patent |
| 1931 HEYES Highway Crossing Protection Patent |
| 1931 LAWRENCE E MURRAY Automatic Railroad Crossing Gate |
| 1931 CRAGO Controlling Highway Crossing Signals |
| 1931 ANDREW Railway Crossing Gate Patent Print |
| 1931 FISHER Design Highway Crossing Signal Patent 49299 |
| 1931 EDGAR Railroad Crossing Gate Art Print |
| 1931 BYRD Railway Crossing Gate Patent Print Art |
| 1931 GRONDAHL Control Highway Crossing Signals |
| 1931 FINN ELLA S DAILEY Railroad Crossing Gate |
| 1931 CHRISTOPHER H OMAN Railroad Crossing Gate |
| 1931 LEES Railroad Crossing Gate Patent Print |
| 1931 UNION Controlling Highway Crossing Signals |
| 1931 MOCK Highway Crossing Signal Patent Print |
| 1931 EVERETT DANIEL Crossing Gate Patent Print |
| 1931 UNION SWITCH SIGNAL CO Highway Crossing Signal |
| 1931 ALPHONSO Automatic Railroad Crossing Gate |
| 1931 SMITH Railroad Crossing Gate Patent Print |
| 1931 VANTASSEL Control Highway Crossing Signals |
| 1931 UNION Control Highway Crossing Signals Art |
| 1931 BAUGHMAN Control Highway Crossing Signals |
| 1931 RUDOLF Level Crossing Gate Patent Print Art |
| 1931 UNION SWITCH SIGNAL CO Highway Crossing Protection |