Green Card Application
Generally speaking, a foreign national intending immigrant can file a Green Card Application only after the Immigrant Visa Petition has been approved by the United States Citizenship and Immigration Service and a Visa number is available.
In the case of the Immediate Relative of a United States citizen, such as a spouse, the Visa is immediately available. Therefore the Green Card Application can be filed concurrently with the Immediate Relative Visa Petition or immediately after it has been approved by the United States Citizenship and Immigration Service.