| Definition: | How many gas and oil fields are in each county, color coded by number. |
| Pale Blue - (1) | |
| Pale Blue - (2) | |
| Pale Green - (3) | |
| Pale Green - (4) | |
| Gray - (5 - 7) | |
| Gray-Green - (8 - 10) | |
| Gray-Green - (11 - 14) | |
| Green-Brown - (15 - 19) | |
| Green-Brown - (20 - 24) | |
| Light Orange - (25 - 30) | |
| Light Orange - (31 - 38) | |
| Light Orange - (39 - 53) | |
| Light Orange - (54 - 83) | |
| Light Orange - (84 - 135) | |
| Orange - (136 - 476) |