Your milkweed may be common milkweed or showy:http://www.monarchwatch.org/milkweed/guide/syriac.htm
Asclepias syriaca (Common)http://www.monarchwatch.org/milkweed/guide/specio.htm
Asclepias speciosa (Showy)
According to Dr. Urquhart in his book, "Monarch Butterfly: International Traveler". Nebraska has 15 species of milkweed (Asclepias):
incarnata, verticillata, pumila, tuberosa, amplexicaulis, syriaca, sullivantii, speciosa, arenaria, latifolia, viridiflora, nuttalliana, stenophylla, engelmanniana, and viridis
The Asclepias speciosa is similar to the syriaca.