70 ILCS 2205/1
Whenever any area of contiguous territory within the limits of two counties, having within its limits two or more incorporated cities or villages, and an aggregate population of not less than 3,500 inhabitants, shall be so situate as to be subject to overflow from any river or tributary thereof, and the maintenance of one or more levees for the protection of the same against such overflow, and of a new or improved outlet for the drainage thereof, will conduce to the preservation of the public health and safety, the same may be incorporated as a sanitary district, in the manner following: Any three hundred legal voters resident within the limits of such proposed district, may petition the circuit court for the county in which the majority of such petitioners reside, to cause the question to be submitted to the legal voters of said proposed district, whether they will organize as a sanitary district under this act. Such petition shall contain the name of such proposed sanitary district, and a definite description of the territory intended to be embraced therein: Provided, no territory shall be included within more than one sanitary district under this act.
70 ILCS 2205/1