Matthew Dixon of Virginia was quickly placed in custody.
No one inside the Empire State Building was injured.
Police say the sword may have been concealed within a cane, but it is still unclear how Dixon got past metal detectors.
Dixon was taken to Bellevue Hospital for observation. He was charged with criminal possession of a weapon.
A building spokesperson released a statement saying.
"Earlier today there was an incident which was resolved without any interruption of Observatory operations or impact to any guests."
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