The earliest mention of commercial activity at 306 E. Main Street is found in “An Illustrated History of San Joaquin County:”
In 1885, O.H. Hull formed a partnership with W.B. Hardacre and J.A. Stewart under the style of Hull Hardacre & Co which… was changed to the Hull & Stewart Company located since April 1 1889 at No 306 Main Street. They handle not only school supplies of all sorts but also sewing machines - The New Crown and Wheeler & Wilson No 9, as well as Crown pianos and organs.
Photos are courtesy of the Bank of Stockton archives.
The Smith & Lang Department Store moved down the street to 306 E. Main in 1915. Smith & Lang would be a significant part of Downtown Stockton for decades to come. Early customers describe the thrill of shopping on three floors, the decorations in the windows and even the “Elevator Attendant” who would call out the departments when the car arrived at its destination. By 1950 the Smith & Lang Company employed 125 people. On July 22, 1958 Smith & Lang burned to the ground in a fire called by Online Archive of California the "worst national mercantile fire of 1958." Insurance claims totaled more than $3,000,000.
On August 25, 1959, Smith & Lang reopened in a building designed by Welton, Beckett and Associates of Los Angeles. In February 1963 Weinstock-Lubin purchased Smith & Lang and the Smith & Lang Company ceased business. On February 12, 1966, Weinstocks closed the Downtown store and moved north to the Weberstown Mall, a move similar to other Downtown merchants: Montgomery Wards, Sears and J.C. Penney’s.
This building remained vacant until 1974 when Katten & Marengo (K&M) moved from 500 East Main St. K&M remained at 306 E. Main Street until 1977. The building was sold in 1982 to developer Philip Wallace who remodeled the building and called it “The Greenhouse Mall.” Today it is known as "The Courthouse Plaza".