What does Genesis 35:20 mean?

Jacob fell deeply in love with Rachel (Genesis 29:20) and worked hard to become her husband. Her death in childbirth would have been especially crushing (Genesis 35:16–19). In memory, Jacob builds a stone pillar over her tomb. Previously, Jacob has built stone pillars to mark places where God appeared to him (Genesis 28:18–19) and to mark his agreement with Laban, Rebekah's father (Genesis 31:44–49). Now he marks the place where his most loved wife (Genesis 29:30) has died.

When the Bible uses the phrase that something is "there to this day," it refers to the time that the passage was physically written down. These words would have been recorded, originally, by Moses. He likely recorded them while Israel was traveling in the wilderness after the exodus from Egypt. This would have been several hundred years later (Exodus 12:41), making the survival of such a monument especially noteworthy. Having said that, the location of Rachel's tomb remained a well-known landmark for many years. It is referred to as a specific place both by Samuel (1 Samuel 10:2) and Jeremiah (Jeremiah 31:15).