Table 01. Number of Metallic Operations in the United States,
by Primary Activity, 1978-2007
|
Year
|
Underground Mines
|
Surface Mines
|
|
|
Underground
|
Surf at UG
|
Total
|
Strip
|
Dredge
|
Other
|
Total
|
|
1978
|
419
|
17
|
436
|
195
|
9
|
7
|
211
|
|
1979
|
438
|
26
|
464
|
222
|
7
|
3
|
232
|
|
1980
|
592
|
71
|
663
|
369
|
10
|
4
|
383
|
|
1981
|
685
|
144
|
829
|
482
|
9
|
1
|
492
|
|
1982
|
551
|
84
|
635
|
388
|
8
|
2
|
398
|
|
1983
|
371
|
40
|
411
|
289
|
9
|
-
|
298
|
|
1984
|
312
|
30
|
342
|
271
|
9
|
-
|
280
|
|
1985
|
258
|
27
|
285
|
259
|
7
|
-
|
266
|
|
1986
|
223
|
31
|
254
|
252
|
8
|
-
|
260
|
|
1987
|
223
|
26
|
249
|
281
|
8
|
-
|
289
|
|
1988
|
216
|
21
|
237
|
295
|
8
|
-
|
303
|
|
1989
|
211
|
22
|
233
|
294
|
7
|
-
|
301
|
|
1990
|
198
|
14
|
212
|
269
|
7
|
-
|
276
|
|
1991
|
143
|
21
|
164
|
220
|
6
|
-
|
226
|
|
1992
|
123
|
16
|
139
|
200
|
7
|
-
|
207
|
|
1993
|
112
|
5
|
117
|
185
|
7
|
3
|
195
|
|
1994
|
117
|
5
|
122
|
148
|
6
|
33
|
187
|
|
1995
|
112
|
6
|
118
|
139
|
6
|
31
|
176
|
|
1996
|
102
|
10
|
112
|
137
|
6
|
23
|
166
|
|
1997
|
97
|
13
|
110
|
133
|
6
|
23
|
162
|
|
1998
|
95
|
10
|
105
|
120
|
5
|
17
|
142
|
|
1999
|
96
|
8
|
104
|
122
|
5
|
13
|
140
|
|
2000
|
86
|
11
|
97
|
110
|
5
|
15
|
130
|
|
2001
|
69
|
|
