Our next stop on 66 is Shamrock, TX... Magnolia Gas Station On 204 N Madden Street, Shamrock. A restored vintage gasoline filling station The Magnolia Petroleum Company was established in 1911; Standard Oil Co. absorbed it in 1925 and by 1959 it was part of their Mobil division. Mobil had already adopted the Pegasus logo in the 1930s.