Could someone help me identify the flower pictured here?

http://www.dwayne.org/UnknownFlower.html

It looks something like cornflower, but the leaves/stems are wrong.

The plant is located in Chantilly, Virginia, and was the first thing
to bloom this spring - around mid-march - and is still blooming. The
plant itself just appeared in our garden last fall (I hate it when
that happens) and bloomed then as well. It never really died off
through the winter.