some persons, places or things from others upon which, but for such limitation, it would operate. The test of a special law is the appropriateness of its provisions to the objects that it excludes. It is not, therefore, what a law includes that makes it special, but what it excludes. If nothing be excluded that should be contained the law is general. Within this distinction between a special and a general law the question in every case is whether any appropriate object is excluded to which the law, but for its limitations, would apply. If the only limitation contained in a law is a legitimate classification of its objects it is a general law.
(Italics ours.) YMCA v. Parish, 89 Wash. 495, 498, 154 P. 785 (1916). Thus, to survive a challenge as special legislation, any exclusions from a statute's applicability, as well as the statute itself, must be rationally related to the purpose of the statute.
Many of the statutes which apply only to municipalities with particular populations delegate governmental powers to those cities. E.g., RCW Title 35 (delegation of powers to first, second, third and fourth class municipalities); RCW 35.20.010 (municipal courts established in cities of over 400,000); RCW 3.46.050 (provision for election of municipal court judges in cities of over 400,000). In this situation, population serves as a rational means of determining which cities have the resources to properly exercise such authority. E.g., State ex rel. Hunt v. Tausick, 64 Wash. 69, 116 P. 651 (1911) (cities with a population of 20,000 to 25,000 may adopt the commission form of government). Other statutes which differentiate on the basis of a municipality's population determine the type or level of services a municipality is required to provide. E.g., RCW 3.12.071 (justices of the peace in cities of 5,000 or more must be attorneys); RCW 3.58.010 (salary for municipal court judge may equal salary for superior court judge in cities of over 400,000). The relationship between population and the level of necessary municipal services is usually clear. E.g., the purpose of the statute is also clear in the following cases: In re Bartz, 47 Wn.2d 161, 168, 287 P.2d 119 (1955) (requirement that a