NEW YORK (AP) — Thirteen works by the American artist N.C. Wyeth, his son Andrew and grandson, Jamie, are heading to a New York City auction.

They come from the collection of Eric Sambol, a New Jersey businessman and nature photographer, and his landscape designer wife, Cynthia.

They acquired their first Wyeth in 2000 — Andrew Wyeth's "Flat Boat."

The May 23 sale at Christie's includes six paintings by Andrew, six by Jamie and one by N.C. Wyeth.

The most expensive piece is Andrew Wyeth's "Rocky Hill." It's a watercolor of the artist's beloved dog, Nell. It's estimated to fetch between $1.8 million and $2.4 million.

The Sambols say they learned that Andrew Wyeth passed away just a few hours after they purchased it on Jan. 16, 2009.