[TheBoiledEgg]

they played on grass at the US Open until 1974
then they played on Har-Tru (green clay) for 3 years
only then did they move to Flushing Meadows to where they are now.

only Jimmy Connors has won titles on all 3 surfaces at the US Open

 

[TheBoiledEgg]

new facilities and its alot cheaper to look after hard courts than it is to look after grass 52 weeks per yr.

also with advent of TV....... NIGHT sessions became possible

also public can use the hard courts to play on as well.
don't think that was allowed on the grass...... you wouldn't want dickheads and plonkers ruining your lawns would you ??