By last count (few years old), the number of dams was estimated at ~84,000 (not 76,000).  Close, but that numerical discrepancy should point out one thing: it&#x27;s an estimate.  USACE maintains an authoritative database of dams in USA (and also 32 in Puerto Rico and 1 in Guam) and the numbers are always a moving target.  Believe at this point they&#x27;re working with pattern matching and satellite imagery to fine-tune the database.  USACE is currently more concerned with inspections near urban populations than cataloging.<p>The write-up is a bit vague and misses one major point: not all of these dams in the U.S. are concrete.  Not even close.  Here&#x27;s a construction type breakdown:<p><pre><code>  70,278 Earth
   9,031 (Unknown)
   1,446 RCC
   1,215 Gravity
     724 Concrete
     455 Other
     420 Rockfill
     201 Masonry
     136 Buttress
     103 Arch
      58 Stone
      51 Timber Crib
      16 Multi-Arch
</code></pre>
Only 847 of those dams are tailings dams, used for industrial processing.  More than 0, but less than 84,000.  Of those, none are listed as concrete (730 Earth, 61 Unknown, 43 Other, 13 Rockfill).