From the link below:
Airplanes - Military - Static Display - Bombers
"The first large-scale production version of the Stratofortress was the B-52D (Model 464-201-7), of which 170 were built between June 1956 and November 1957. The B-52D was externally indistinguishable from the B-52C which preceded it. The only significant internal difference was the adoption of the MD-9 fire control system as fitted to the final B-52C. The powerplants were the J57-P-19W or -29W. In contrast to the B-52C, which was readily convertible to the reconnaissance configuration, the B-52D was built exclusively for the long-range bombing role.
The B-52D was the first Stratofortress to be built at two different locations. 69 examples were built at Boeing's Wichita, Kansas facility, with the remainer being built in the main Boeing plant in Seattle. The Wichita plant had originally been owned by the Stearman Aircraft Company but had been acquired by Boeing in 1934 and became a Boeing division in 1939. It had been used during World War 2 as an inland site for B-29 manufacture. The decision to shift B-52 production from Seattle to Wichita was a result of several factors. The commercial business at Seattle was picking up and Boeing needed more plant space to handle the orders. It so happened that there was a large, well-qualified work force already at hand in Wichita which was working on the B-47, the production of which was winding down. "