King County adopted its first zoning code in 1937. Two years earlier, in the 1935 Planning Commissions Act, the state Legislature had authorized counties, cities, and towns to establish planning commissions and to regulate and restrict land use and development, provided that they did so by means of a comprehensive plan that applied throughout the jurisdiction or a specified subsection. The law also required that the resolution adopting the plan along with any map referred to in it should be filed with the county auditor.
Through the 1940s, the Planning Commission prepared maps, which were approved and adopted by the County Commissioners, showing the location of different use districts established in the 1937 zoning resolution and subsequent revisions. In 1949 the Commission hired professional planning staff and initiated preliminary studies for preparing a comprehensive plan. During the 1950s, the planning staff published a series of 14 area reports, covering the entire County outside of incorporated cities and towns, based on detailed studies for a comprehensive plan.
However, on July 25, 1958, King County Superior Court Judge Malcolm Douglas ruled that the Planning Commission had never filed an adequate comprehensive plan with the County Auditor as required. The ruling effectively meant that the County had been zoning illegally since 1937. Although the County could have appealed the ruling to the state Supreme Court (and might have won -- in fact in 1964 the Supreme Court held that Seattle's zoning was valid even though it had not followed all the procedural requirements of the Planning Commissions Act), it was decided instead to adopt new resolutions.
The Planning Commission quickly prepared a "generalized comprehensive plan text and map of the whole county" (Progress Report 1958-1959), which it based on the area studies conducted earlier in the decade. On August 11, 1958, less than three weeks after Judge Douglas ruled, the Board of County Commissioners enacted Resolution No. 18800, the comprehensive zoning plan. The plan text and map were filed with the County Auditor the same day. The next day the Commissioners enacted Resolution No. 18801, the zoning code. Given that Judge Douglas's ruling called earlier measures into doubt, the two resolutions constituted the County's first unquestionably valid comprehensive plan and zoning, even though it had been zoning since 1937.
Although Resolution No. 18800 may be considered King County's first valid comprehensive plan, the type of comprehensive zoning plan contemplated by the Planning Commissions Act and enacted in 1958 differed from later comprehensive plans. When the concept of zoning was first developed early in the twentieth century, it was often referred to as comprehensive zoning because zoning controls applied to an entire area and comprehensively addressed a whole range of land-use issues, as opposed to more specific health and safety laws that prohibited or regulated only one particular activity or land use. Thus the Planning Commissions Act requirement that "[a]ll regulations shall be worked out as parts of a comprehensive plan" simply made clear that zoning regulations would be structured to deal with location of residential, trade, industrial, and other uses, building size and setbacks, population densities, and related matters as a package.
As planning became more sophisticated over the years, the concept of a comprehensive plan evolved. Rather than being simply the structure within which zoning controls were organized, the comprehensive plan came to be a separate statement of general policy, a "blueprint" that guided the subsequent adoption of specific zoning regulations. King County's next comprehensive plan, which was adopted in 1964, was one of the first of such "policy plans."