Total Recreation Visits to National Parks by Year:

1924: 4,660,300
1925: 5,622,200
1926: 6,022,200
1927: 6,136,800
1928: 6,550,300
1929: 7,132,100

1930: 6,910,900
1931: 8,073,900
1932: 7,895,800
1933: 8,165,500
1934: 8,580,800
1935: 9,718,300
1936: 10,781,100
1937: 11,832,600
1938: 14,495,200
1939: 14,331,900

1940: 16,162,900
1941: 18,004,900
1942: 10,407,200
1943: 6,274,600
1944: 7,152,000
1945: 10,074,100
1946: 18,240,600
1947: 21,330,800
1948: 24,010,800
1949: 26,080,200

1950: 27,367,800
1951: 29,950,200
1952: 33,006,900
1953: 35,403,000
1954: 40,303,900
1955: 45,712,800
1956: 52,556,000
1957: 60,957,500
1958: 68,449,500
1959: 81,521,000

1960: 92,595,500
1961: 101,912,500
1962: 112,762,200
1963: 122,582,000
1964: 133,762,300
1965: 160,336,100
1966: 150,728,900
1967: 149,647,100
1968: 156,665,300
1969: 162,838,100

1970: 172,554,500
1971: 178,109,500
1972: 183,958,300
1973: 188,174,600
1974: 192,915,800
1975: 199,200,800
1976: 199,928,100
1977: 204,797,400
1978: 218,494,300
1979: 220,165,600

1980: 233,549,300
1981: 235,709,200
1982: 233,437,500
1983: 227,707,800
1984: 227,553,900
1985: 225,407,300
1986: 226,532,700
1987: 238,458,300
1988: 242,315,700
1989: 252,495,000

1990: 263,050,600
1991: 278,849,000
1992: 287,690,500
1993: 295,473,100
1994: 330,348,400
1995: 345,082,900
1996: 341,204,000

Source:

"National Forest Recreation Use, 1924-1996"; from U.S. Forest Service website, (PDF)