This little vetch is in full bloom right now; you can see it everywhere. Low twining vines sport one to three magenta flowers, nestled among feathery leaves.
Spring vetch (Vicia sativa) is a nitrogen fixer in the pea family that was introduced to the US from Europe and North Africa. The leaves, seeds, shoots and pods are all edible; according to Wikipedia, evidence from Neolithic sites in the Middle East suggest it was a part of the local diet of the time. It has also been reported from predynastic sites of ancient Egypt and several Bronze Age sites in Turkmenia and Slovakia. However, definite evidence for later vetch cultivation is available only for Roman times. If you trust Wikipedia, that is.
It is also known as garden vetch and common vetch.