Why is our homeland so important to us? Why are memories so important to us? Why are our family roots so important to us?
Antonia means all these to Jim: she is Nebraska, she is his young past, she is the matriarch of self-sufficient pioneer women, she is the embodiment of the land from which he loved, she is Innocence, she is even a kind of American Dream: loyal, proud, and indefatigable.
Now that Jim is older, childless, and unhappy, he looks back to the past, to his early days in Nebraska when he was 10 and Antonia was 14. It was then that she gave him a ring. It was then that they were effectively married (at least in memory), and years later, when he returns, she is the same. Don't we all wish to return to our first love when our current love has worn thin?
Speaking of Antonia, Jim ends his memoir with these lines:
...she still had that something which fires the imagination.... All the strong things of her heart came out in her body.... She was a rich mine of life, like the founders of early races.