I found this growing in my back yard and am curious as to what it is.
your plant is one of the Trilliums. It could be one of several species, and I cannot be more specific without flowers. The deep rich colors on the leaves are found in Trillium maculatum, as well as a few others such as T. underwoodii and T. reliquum. Your location would have helped me more.
Steven Hill, Ph.D., Botanist, SCNPS