Background...

The woman in the painting is Anna Christina Olson (May 3, 1893 – January 27, 1968). Anna had a degenerative muscular disorder which meant that she had not been able to walk since she was about 30 years old.[2] She was firmly against using a wheelchair, so she would crawl everywhere. Wyeth was inspired to create the painting when he saw her crawling across a field while he was watching from a window in the house.He had a summer home in the area and was on friendly terms with Olson.

but she was not the primary model; Wyeth's wife Betsy posed as the torso of the painting.