 The museum opened in 2001 , two months after the September 11 attacks . The museum 's visitor attendance was much lower than what was projected ; the museum partially attributed that to the depressed tourist economy stemming from the attacks . 
 The museum opened in 2001 , two months after the September 11 attacks . The museum <a href='null_genetive' title='1'><mark>'s</mark></a>visitor attendance was much lower than what was projected ; the museum partially attributed that to the depressed tourist economy stemming from the attacks . 
Da museum opened in 2001 , 2 months after the September 11 attacks . The museum  visitor attendance was much lower den what was projected ; the museum partially attributed dat to the depressed tourist economy stemming from tdaattacks .