| Year | National Wilderness Preservation System | National Wild and Scenic River System |
| million acres | river miles | |
| 1968 | 10.03 | 773 |
| 1969 | 10.19 | 773 |
| 1970 | 10.40 | 868 |
| 1971 | 10.40 | 868 |
| 1972 | 11.03 | 895 |
| 1973 | 11.03 | 961 |
| 1974 | 11.38 | 1,018 |
| 1975 | 12.72 | 1,145 |
| 1976 | 14.45 | 1,610 |
| 1977 | 14.49 | 1,610 |
| 1978 | 19.00 | 2,299 |
| 1979 | 19.00 | 2,299 |
| 1980 | 79.71 | 5,662 |
| 1981 | 79.84 | 6,908 |
| 1982 | 79.88 | 6,908 |
| 1983 | 80.21 | 6,908 |
| 1984 | 88.55 | 7,217 |
| 1985 | 88.70 | 7,224 |
| 1986 | 88.80 | 7,363 |
| 1987 | 88.99 | 7,709 |
| 1988 | 90.81 | 9,264 |
| 1989 | 91.46 | 9,281 |
| 1990 | 94.97 | 9,318 |
| 1991 | 95.03 | 9,463 |
| 1992 | 95.39 | 10,295 |
| 1993 | 95.44 | 10,516 |
| 1994 | 103.72 | 10,734 |
| 1995 | 103.60 | 10,734 |
| 1996 | 103.60 | 10,815 |
| 1997 | 103.60 | 10,815 |
| 1998 | 104.57 | 10,896 |
| 1999 | 104.75 | 10,931 |
| 2000 | 104.76 | 10,955 |
Sources: Landres, P. and S. Meyers. A National Wilderness Preservation System Database: Key Attributes and Trends, 1964-1999. Gen. Tech. Rep. INT-GTR-18-Revised Edition (U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Ogden, UT, 2000).
U.S. Department of Agriculture, Forest Service, National Wilderness Preservation System Database (an Internet accessible database, as of October 25, 2000).
U.S. Department of the Interior, National Park Service, River Mileage Classifications for Components of the National Wild and Scenic River System (an Internet accessible data table, as of October 25, 2000).
Notes: Data reflect year-end cumulative totals, except for current year data.
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