Except for Emily Dickenson, who is an outlier and should not be counted.

Seriously, she used dashes all the time. Here is a direct copy and paste of the first two stanzas of her poem "Because I count not stop for Death" from the first source I found, https://www.poetryfoundation.org/poems/47652/because-i-could...

  Because I could not stop for Death –
  He kindly stopped for me –
  The Carriage held but just Ourselves –
  And Immortality.

  We slowly drove – He knew no haste
  And I had put away
  My labor and my leisure too,
  For His Civility –

Her dashes have been rendered as en dashes in this particular case rather than em dashes, but unless you're a typography enthusiast you might not notice the difference (I certainly didn't and thought they were em dashes at first). I would bet if I hunted I would find some places where her poems have been transcribed with em dashes. (It's what I would have typed if I were transcribing them).