Wash. Const. art. XII, § 19

Any association or corporation, or the lessees or managers thereof, organized for the purpose, or any individual, shall have the right to construct and maintain lines of telegraph and telephone within this state, and said companies shall receive and transmit each other's messages without delay or discrimination and all of such companies are hereby declared to be common carriers and subject to legislative control. Railroad corporations organized or doing business in this state shall allow telegraph and telephone corporations and companies to construct and maintain telegraph lines on and along the rights of way of such railroads and railroad companies, and no railroad corporation organized or doing business in this state shall allow any telegraph corporation or company any facilities, privileges or rates for transportation of men or material or for repairing their lines not allowed to all telegraph companies. The right of eminent domain is hereby extended to all telegraph and telephone companies. The legislature shall, by general law of uniform operation, provide reasonable regulations to give effect to this section.