To my knowledge, as I have been told, the pieces of I-beam are from the remains of the World Trade Center.
Reunited... to imply to joining of the two pieces of which had been previously separated ...to relate to how the tragic event brought the country together ...to relate to how those who perished during the attack have since been reunited to the right hand of God or Deity.
It is a very quiet and solemn piece to behold. Its appears to be in action of uniting, but it is still and paused. The wounds exhibited by the event have not been fixed or are in the processing of healing. The pieces of I-beam were once of each other as can be witnessed by the relation of cut marks along their edges. A majority of the surface, although cleaned, was left intact so as not to erase their history or significance as every mark made and left on the sculpture is a testimonial to its journey.