Thanks to Leapfrog (Art), I know this samara came from an Ash tree, though I didn't see the tree. I'll have to go back and examine all the trees in that area so I can find it! I saw it land here but when I looked up, I could only see trees that couldn't have dropped it--Oaks and Madrones. I am very interested to take a closer look! :)

This kind of seed dispersal shape is called a "samara". which holds a seed and forms a "wing" to help carry it away from the parent tree.

From Wiki: en.wikipedia.org/wiki/Samara_(fruit)
A samara is a type of fruit in which a flattened wing of fibrous, papery tissue develops from the ovary wall. A samara is a simple dry fruit and indehiscent (not opening along a seam). It is a winged achene. The shape of a samara enables the wind to carry the seed farther away than regular seeds from the parent tree:

The seed can be in the centre of the wing, as in the elms (genus Ulmus), the hoptree (Ptelea trifoliata), and the bushwillows (genus Combretum).
The seed can be on one side, with the wing extending to the other side, making the seed autorotate as it falls, as in the maples (genus Acer) and ashes (genus Fraxinus).
A samara is sometimes called a key and is often referred to as a whirlybird, helicopter, whirligig, polynose, or, in the north of England, a spinning jenny. During the autumn months, they are a popular source of amusement for children who enjoy tossing them in the air and watching them spin to the ground.

Some species that normally produce double samaras, such as Acer pseudoplatanus, can also produce a few multi-lobed samaras with 3 or 4 seeds.