Deb,
It looks like Paeonia lutea:
https://www.kelways.co.uk/prod...
They get bigger than common cultivars and hybrids. Paeonia lutea is a parent of some most beautiful tree peonies, such as High Noon and Souvenir de Maxime Cornu.
http://www.peonysoc.com/lutea%...
Yours has just started blooming and, from this point, the plant can only bloom more in years to come. Hope you will keep this beautiful peony in your garden.
