Final answer:
The state with the Wisconsin River, Dells, and other rivers mentioned, all contributing to the Mississippi River, is Wisconsin, which became a state in 1848.
Step-by-step explanation:
The state in question, which contains the Wisconsin River with its notable Dells, and serves as a tributary to the Mississippi River, is Wisconsin. The Wisconsin River is known for its scenic region known as the Dells. The Mississippi River forms the southern boundary between Wisconsin and Minnesota, with various other rivers mentioned such as the St Croix River, Chippewa River, Menominee River, and Montreal River also located within or along the borders of Wisconsin. Wisconsin became a state in 1848 and has a diverse river system that contributes to its geography and historical development.