| State | Age of containing rocks | Base | Production for 1919 (barrels) | Total production including 1918 (barrels) |
| Alaska | East-Low. Tertiary | Paraffin | (a) | (a) |
| West-Jurassic | ||||
| California | Cretaceous: Tertiary | Ashpalt | 97,531,997 | 1,110,226,576 |
| Colorado | Pierre-Cretaceous | Paraffin | 143,286 | 11,319,370 |
| Illinois | Mississippian-Pennsylvanian | Paraffin | 13,365,974 | 298,225,380 |
| Indiana | East-Ordovician (Trenton) | Paraffin | 877,558 | 106,105,584 |
| West-Pennsylvanian | ||||
| Kansas | Pennsylvanian | Par.-Asph. | 45,451,017 | 148,450,298 |
| Kentucky, | Mississippian | Paraffin | 4,376,342 | 18,213,188 |
| Tennessee | ||||
| Louisiana | Cretaceous-Quat. | Paraffin | 16,042,600 | 150,769,911 |
| Cretaceous-Eocene | ||||
| Michigan, | Carboniferous | Paraffin | (a) | (a) |
| Missouri | ||||
| Montana | — | — | 69,323 | 213,639 |
| New Mexico | Carboniferouos-Cretaceous | — | (a) | (a) |
| New York, | Devonian-Carboniferous | Paraffin | 8,216,655 | 788,202,717 |
| Pennsylvania | ||||
| Ohio, East | Ordovician-Carboniferous | Paraffin | 7,285,005 | 463,367,386 |
| and West | ||||
| Oklahoma | Pennsylvanian | Paraffin | 103,347,070 | 851,320,457 |
| Texas | Pennsylvanian, Cretaceous-Quat. | Asph.-Par. | 38,750,031 | 327,550,005 |
| Utah | — | — | (b) | (b) |
| West Virginia | Devonian-Carboniferous | — | 7,866,628 | 294,474,710 |
| Wyoming | Carboniferous-Cretaceous | Asph.-Par. | 12,596,287 | 40,019,573 |
| Other | — | — | 7,943 | 112,925 |
| 355,927,716 | 4,608,571,719 | |||
| (a) Included in "Other." | (b)Included in Wyoming. | |||
Fig. 7. Chart showing the present tendency of the United States in respect to its unmined reserve of petroleum. Data from U.S. Geological Survey. After Gilbert and Pogue.[ToList]
Methods of estimating reserves. It may be of interest to inquire into the basis on which predictions are made of the life of an oil pool. The process is essentially a matter of platting curves of production, and of projecting them into the future with the approximate slopes exhibited in districts which are already approaching exhaustion.[21] While no two wells or two districts act exactly alike, these curves have group characteristics which are used as a rough basis for interpreting the future.
Fig. 8. The annual output of the principal oil fields of the United States for the last twenty years. Data from U.S. Geological Survey.[ToList]