My historical data shows the following prices for the SPX...
On Sept 10th, 2001, the SPX closed @ 1092.54.
When the market re-opened on Sept 17th, the SPX Open, High, Low, Close prices were:
O = 1092.54
H = 1092.54
L = 1037.46
C = 1038.77
I don't remember the details of the Sept...