 Lehman Brothers originally took half the floor area in 1 William Street, but then occupied additional space vacated by tenants with expiring leases, as well as space in two adjacent buildings.By the 1970s, Lehman Brothers was seeing financial losses, and under chairman Peter G. Petersen, the company merged with Kuhn, Loeb & Co. in 1977.The combined company moved out of the building at the end of 1980, putting the structure on sale for $10 million and consolidating its operations at another facility on 55 Water Street.