As a death-haunted poet, the voice in "Because I Could Not Stop for Death" is, indeed, that of Emily Dickinson.
It is estimated that over half of Dickinson's poems are concerned with death, and one-third are centrally thematic of death. Having lived in a small town in New England in the mid-nineteenth century, a time in which there was a high mortality rate for young people, there were, as a consequence, often scenes of death in families that contributed to Dickinson's preoccupation with this subject. Also, since she was so reclusive, hers was in some sense, a living death as she suffered anguish over her missing out on romantic love, and so she became preoccupied with death. However, critics agree that the borderline between Dickinson's treatment of death and her "affirmation of immortality" cannot be defined with clarity.
"Because I Could Not Stop for Death" is a poem in which the speaker is almost seduced by death as, at first, the speaker feels that Death is gentlemanly as it calls upon her with a carriage and carries her past the activities of one's lifetime, performed during youth, maturity, and age with the imagery of children at play, the fields of mature grain, and the setting sun. It is only in the final stanza that the realization comes to the speaker that she is on a journey toward death:
Since then--'tis Centuries...
I first surmised the Horses' Heads
Were toward Eternity--