The present inventions provide mammalian cells that comprise multiple Stable Integration Sites. The inventions provide sites introduced genomically into a Genomic Safe Harbor and introduced genomically outside of that particular Genomic Safe Harbor, including but not limited to another Genomic Safe Harbor. Polynucleotides of interest that encode polypeptides or RNAs of interest can be inserted into the Stable Integration Sites provided according to the inventions. The cells and methods of the inventions can be used for the high yield production of any protein, including viral proteins. Additionally, the cells and methods of the inventions are useful for production of viral vectors, such as AAV, antibodies and other proteins.