I'll 1-up you on that one: While technically not a dam, the Dutch Afsluitdijk is 20 miles long, and was finished in 1932.

Speaking of the Turing Award, why isn't Alan Turing on the list of famous programmers?
I realise that it is up for debate whatever he was a programmer by modern standards, but there simply weren't any good computers to program on in his days. However, he (probably) wrote the first computer Chess-program in 1948, for a computer that didn't even excist at the time.
He deserves to be on the list, IMHO.