Flower:

2 to 9 flowers in loose clusters (racemes) arising from leaf axils in the upper part of the stem. Individual flowers are a typical shape for a member of the pea family, slightly elongated, ½ to ¾ inch long. Flower color ranges from pink to purple to blue. The calyx holding the flower is hairless to minutely hairy, with 5 broadly triangular lobes, the lower lobes up to twice as long as the short upper lobes, and all rather shorter than the calyx tube. Flower stalks are minutely hairy. 

Leaves and stem:

Leaves are compound with 4 to 8 pairs of leaflets and a tendril at the end of the leaf that winds around other plants for support. At the base of the stalk is a pair of leafy appendages (stipules) that are up to 1/3 inch long, sharply pointed at both ends, with 3 sharp teeth in the lower half. Leaflets are narrowly egg-shaped to oblong-elliptic and may have rounded, blunt or pointed tips. Each is up to 1½ inch long and about ¼ inch wide, toothless and hairless, becoming smaller towards the end of the leaf. Stems are angled, hairless, and branched.

Fruit:

Fruit is a pea-shaped pod, about 1 inch long, that turns from green to reddish brown as the fruit ripens. Pods contain an average of 10 seeds.

Notes:

There are several members of the pea family that are climbing vines with racemes of purplish or pinkish flowers. One major distinguishing feature is the stipule at the base of the leaf stalk, which is unique for many species; American Vetch is unique with the 3 sharp teeth on the lower half of the stipule. The non-native vining vetches tend to create dense, tangled masses where American Vetch is more spindly, with fewer flowers in looser clusters. When not in bloom, American Vetch plants with rounded leaflets might be mistaken for Crown Vetch (Coronilla varia), but Crown Vetch has no tendril at the end and its stems are leafier, plus Crown Vetch has round flower clusters.

There are 3 recognized subspecies (or vars, depending on the reference) of Vicia americana, 2 of which are found in Minnesota, though most herbarium records are not identified to a specific subspecies/var: subsp. americana is likely widespread, subsp. minor is likely less common. The differences between the two are not well documented but minor may have thick, proportionately narrower leaflets that are oblong-elliptic, and 4 or fewer flowers per cluster, with subsp. americana having broader, thin leaflets that are more lance-elliptic to egg-shaped, and 4 or more flowers per cluster. From some subsp. minor herbarium records I've examined, the lower leaves may be as described and the upper leaves more like subsp. americana, so check the whole plant before deciding which one you might have.