According to Pa state law, is a husband and wife business considered a partnership or can it be a sole proprietorship? Where can I find the answer?

It would have to be a partnership. Here is a link from the state website that defines a sole proprietorship as being owned by 'one natural person.'

You want to run this by your bank's attorney. Our bank does open husband-wife sole-proprietorship accounts operating as an unincorporated business. Our bank's attorney approved this action.