Why is Kansas (the city) not located within Arkansas (the state) and why aren't they pronounced the same way?

Not sure if there is any strange about the location of Kansas City, the location was chosen by French fur traders in the early 1800's.

The origins of Kansas City date to the early 1800s, when French fur traders arrived by the Missouri River and built rough cabins along the river. The town of Kansas was formed in 1838 and a trail connecting the river landing to the Santa Fe Trail in the town of Westport was established.

https://www.historickansascity.org/kansas-city/

The names Arkansas and Kansas is a bit easier to address, the simply derive from different Native American langues.

According to Arkansas Secretary of State's website, the name "Arkansas" originates with the native American Quapaw tribe "by way of early French explorers. The explorers met a group of Native Americans known as the Ugakhpah (which means "people who live downstream"). These Native Americans later were called the Quapaw, who were also called the Arkansaw. This name came to be used for the land where these Native Americans lived."

https://statesymbolsusa.org/symbol-official-item/arkansas/name-origins/origin-arkansas

The name "Kansas" comes from the native American Kaws or Kansa people (a Sioux tribe). According to Kansas Historical Society; "The Kaw tribe derived its name from the Siouan aca, "Southwind." Among the many variations of the name given by French traders and other Europeans were "Kanza" or "Kansa." By the mid-18th century, the "People of the Southwind" were the predominant tribe in what became the state to which they gave their name."

https://statesymbolsusa.org/symbol-official-item/kansas/name-origins/origin-kansas

To supplement the previous answer, the Arkansas pronunciation preserves the way it was said in French, with a silent final 's'. Kansas, on the other hand, appears to have been pluralised at some point with the pronounced 's' the English use. Of further note is that the largest and best-known Kansas City is in Missouri, across the Missouri River from Kansas City, Kansas, at the Missouri's confluence with the Kansas River. There are also places called Arkansas City in Arkansas (near the Mississippi River) and in Kansas (on the upper part of the Arkansas River).

"Kansas" came to English from a Native American language. "Arkansas" came to English from the same word in the same language, but via French. In French, the final /s/ that is the plural marker is weakened or elided, so we don't pronounce it in the English word "Arkansas".


https://www.quora.com/Americans-why-is-Kansas-pronounced-Kan-SAS-but-Arkansas-pronounced-Ar-Kan-saw-It-really-pickles-my-brain#:~:text=%E2%80%9CKansas%E2%80%9D%20came%20to%20English%20from,the%20English%20word%20%E2%80%9CArkansas.%E2%80%9D