>> paula grant berry: there were lots of issues. >> iken: oh, boy. lots, lots. >> stahl: tonight we'll take you back to the challenges of creating our nation's 911 museum. >> mike anderson: not a day goes by where i don't think about my son. he was mike jr. he was my only son. his son, mike anderson, jr., a marine, was killed in iraq. now, the father sees it as his duty to help other gold star parents at this remarkable event. the burden that you have is unbearable. >> anderson: at times, yes, sir. >> pelley: but when you come to this event, you take on the unbearable burdens of another 100 families. >> anderson: my son went abroad to help people h it is human nature to want to help others. >> bill whitaker: it may surprise you to hear that oklahoma is the most earthquake- prone state in the continental u.s. >> whoa! >> whitaker: in 2009, there were, on average, two earthquakes per year of magnitude three or greater. last year, there were 907. what's more astonishing is that nearly all of oklahoma's earthquakes are manmade. >> kathy matthews: i use t

paula grant berry's husband david worked in tower 2, as did monica iken's husband, michael. anthoula katsimatides' brother john was in tower 1, and tom roge?r's daughter jean was a flight attendant on american airlines flight 11. >> paula grant berry: the site radiates something for us all in a very special way. >> iken: that's where the final resting place of our loved ones >> iken: it has to be there. >> has to be there. >> anthoula katsimatides: yes. >> monica iken: and you can feel it. >> greenwald: this is the remnant of the exterior structure that made up the twin towers. >> stahl: one of greenwald's first challenges in this hallowed space was deciding where the story of 9/11 should begin. >> greenwald: we begin with the voices of people from around the world, remembering where they were when they heard about the attack. >> someone barged in and said, "oh, my god, a plane has just crashed into the world trade center." >> stahl: the idea is to will bring their own memories of 9/11, which was witnessed within hours by people all across the globe. >> phone rang, woke me u

>> paula grant berry: there were lots of issues. >> iken: oh, boy. lots, lots. >> stahl: tonight we'll take you back to the challenges of creating our nation's 911 museum. >> mike anderson: not a day goes by where i don't think about my son. he was mike jr. he was my only son. >> pelley: he is what is known his son, mike anderson, jr., a marine, was killed in iraq. now, the father sees it as his duty to help other gold star parents at this remarkable event. the burden that you have is nbearable. >> anderson: at times, yes, sir. >> pelley: but when you come to this event, you take on the unbearable burdens of another 100 families. >> anderson: my son went abroad to help people he never met. help others. >> bill whitaker: it may surprise you to hear that oklahoma is the most earthquake- prone state in the continental u.s. >> whoa! >> whitaker: in 2009, there were, on average, two earthquakes per year of magnitude three or greater. last year, there were 907. what's more astonishing is that nearly all of oklahoma's earthquakes are manmade. >> melinda olb

>> paula grant berry: there were lots of issues. >> iken: oh, boy. lots, lots. >> stahl: tonight we'll take you back to the challenges of creating our nation's 911 museum. >> mike anderson: not a day goes by where i don't think about my son. he was mike jr. he was my only son. >> pelley: he is what is known

>> paula grant berry: there were lots of issues. >> iken: oh, boy. lots, lots. >> stahl: tonight we'll take you back to the challenges of creating our nation's 911 museum. >> mike anderson: not a day goes by where i don't think about my son. he was mike jr. he was my only son. >> pelley: he is what is known

>> paula grant berry: there were lots of issues. >> iken: oh, boy. lots, lots. >> stahl: tonight we'll take you back to the challenges of creating our nation's 911 museum. >> mike anderson: not a day goes by where i don't think about my son. he was mike jr. he was my only son. >> pelley: he is what is known

>> paula grant berry: there were lots of issues. >> iken: oh, boy.s, lots. >> stahl: tonight we'll take you back to the challenges of creating our nation's 911 museum. >> mike anderson: not a day goes by where i don't think about my son. he was mike jr. he was my only son. >> pelley: he is what is known as a gold star parent, because

>> paula grant berry: there were lots of issues. >> iken: oh, boy. lots, lots. >> stahl: tonight we'll take you back to the challenges of creating our nation's 911 museum. >> mike anderson: not a day goes by where i don't think about my son. he was mike jr. he was my only son.

paula grant berry's husband david worked in tower two, as thula's brother john wasn's daun was a flight attendant on flight 11. >> the site radiates something for us all. >> the final resting place of ou is. awe hauz >> has to be there. >> you can feel it. >> remnant of the extear year vuk chu structure. >> one of the first challenges in the hall lowed s begin. >> we begin with the voiceswled will bring their own memories of 9/11. witnessed within hours by people all across the globe. >> the phone rang -- my business partner told me to turn on the greenwald said we are all survivors of 9/11. it is fitting visitors would descend to the main exhibits of the museum beside an enormous staircase here encased in wood that served as an escape route. >> on 9/11. hundred ran to safety down this stair. >> so-called survivor stas case was one of several artifacts so big the museum had to be built around them. like this fire engine. lowered in through a hatch in the roof to honor first responders. 441 of whom lost their lives. and the final last column. the final massive remnant of the towers to be

paula grant berry's husband david worked in tower two, as tower one. and tom rogert's daughter jean was a flight attendant on flight 11. >> the site radiates something for us all. >> the final resting place of our loved ones is. >> has to be there. >> you can feel it. >> remnant of the extear year structure. >> one of the first challenges in the hall lowed space was where the story of 9/11 should begin. people around the world. >> i was driving to work. >> remembering where they were when they heard about at take. >> someone barged in. and said, oh my god, a plane crashed into the world trade center. >> acknowledge each visitors will bring their own memories of 9/11. witnessed within hours by people all across the globe. >> the phone rang -- my business television. greenwald said we are all survivors of 9/11. it is fitting visitors would descend to the main exhibits of the museum beside an enormous staircase here encased in wood that served as an escape route. >> on 9/11. hundred ran to safety down this stair. >> so-called survivor stas case was one of

>> paula grant berry: there were lots of issues. >> iken: oh, boy. lots, lots. >> stahl: tonight we'll take you back to the challenges of creating our nation's 911 museum. >> mike anderson: not a day goes by where i don't think about my son. he was mike jr. he was my only son. >> pelley: he is what is known his son, mike anderson, jr., a marine, was killed in iraq. now, the father sees it as his duty to help other gold star parents at this remarkable event. the burden that you have is unbearable. >> anderson: at times, yes, sir. >> pelley: but when you come to this event, you take on the unbearable burdens of another 100 families. >> anderson: my son went abroad it is human nature to want to help others. >> bill whitaker: it may surprise you to hear that oklahoma is the most earthquake- prone state in the continental u.s. >> whoa! >> whitaker: in 2009, there were, on average, two earthquakes per year of magnitude three or greater. last year, there were 907. what's more astonishing is that nearly all of oklahoma's earthquakes are manmade. >> melinda o

>> paula grant berry: there were lots of issues. >> iken: oh, boy.s. >> stahl: tonight we'll take you back to the challenges of creating our nation's 911 museum. >> mike anderson: not a day goes by where i don't think about my son. he was mike jr. he was my only son. >> pelley: he is what is known