On March 25, 1965, President Johnson issued Executive Order No. 11210, which established the Temporary Commission on Pennsylvania Avenue. The Temporary Commission was charged with analyzing the engineering, financial, planning, and other relevant considerations essential to ensuring the adoption and implementation of the 1964 master plan, as well as recommending appropriate legislation to the President and Congress. The Temporary Commission was also instructed to coordinate its efforts with the National Capital Planning Commission's master plan for the city. The Temporary Commission was an interim measure designed to ensure that no buildings incompatible with the plan were built until legislation regarding the master plan was passed. Although certain aspects of the master plan were controversial among some groups, the District of Columbia enacted zoning changes to permit mixed-used development and buildings which conformed to the Owings plan in April 1965. Construction of the first private building under the master plan, 451 12th Street NW, began in August 1965. Legislation to make the Temporary Commission permanent and give it extensive powers was introduced in October 1965, but strong opposition to the proposed National Plaza emerged and hindered passage of the bill. The size of the plaza remained intact into late 1967, and a large new arts and office building (to be built between 11th and 13th Streets NW on E Street NW) was proposed.