Is the plant pictured to the right poison ivy?
No, it is Virginia Creeper. Notice the leaves.
You will find this plant in the same types of habitat as Poison Ivy. It is easy to distinguish from poison ivy by its 5 leaflets on a palmately-compound leaf. Unlike poison ivy, it will not harm you. The bark of the woody vine has been used as a tonic, expectorant and remedy for dropsy.
"Leaves of three, let it be" is a good rule to follow but some plants with 3 leaves are ok.
Leaves are usually found in threes with an end leaf along the vine. This plant is scattered throughout Missouri in old fields, prairies, open banks and along roadsides, similar to the location of poison ivy vines.
I have a memory of picking dewberries in late summer and often encountering a snake.
Here is a close up view of the poison ivy vine. It can be found all over Missouri. Notice the three, smooth leaflets. The leaf margins are largely toothed. The end leaflet has a more pronounced pointed tip. An oil found in all parts of the plant is poisonous and can produce an intense skin irritation. Wash with cold, soapy water immediately after contact with this plant.