The name "Arkansas" reflects both French and Native American heritage. Kansas and Arkansas stem from the same root word (kká:ze) which was a Siouan term referring to members of the Dhegiha branch of the Siouan family. It was also used to describe the Kansa tribe in the state that would become Kansas. It's believed to mean "people of the south wind."
Some of the first settlers of the state were French. French settlers heard the Quapaw call the natives Arkansa. So, the French were first to reference Arkansas in writing as "Arkansaes" and "Arkancas." French spelling often adds a silent S to the end of words. The Arkansas Gazette set precedence for spelling it Arkansas in print.
So, why don't we say ar-KAN-zuhss then? If it's the same word, shouldn't it be pronounced the same? According to Historians, it's Kansas that's wrong in the pronunciation, not Arkansas natives. Historians argue that "KAN-zuhss" is clearly the English way to pronounce and spell the word, whereas we pronounce it correctly, even though we spell it the French way.
Historians get pretty serious about this. There is a 30 page document that recounts the meeting of the Historical society of the state of Arkansas, and the Eclectic society, of Little Rock, Ark. in 1881 about this very issue.
It is clear, then, that the name Kansas is spelled in English, while the name Arkansas is of French orthography, and that the two names should not be pronounced alike...
The present spelling clearly indicates the nationality of the adventurers who first had the hardihood to explore this vast extent of country. The present dictionary mode of pronouncing the word does violence to the first historic fact, and to drop this and then change the spelling would do violence to the second historic truth. Both truths are worthy of preservation.
So, saying Ar-KAN-zuhss does violence to the historic facts. You got that, out-of-towners? The Arkansas General Assembly was actually called on to rule on the pronunciation of the state name, with the Historical Society's help.
Be it therefore resolved by both Houses of the General Assembly, That the only true pronunciation of the name of the State, in the opinion of this body, is that received by the French word representing the sound ; and that it should be pronounced in three syllables, with the final "s" silent. The "a" in each syllable with the Italian sound, and the accent on the first and last syllables, being the pronunciation formerly universally and now still most commonly used ; and that the pronunciation with the accent on the second syllable, with the sound of "a" in man, and the sounding of the terminal " s " is an innovation to be discouraged.
That wording can actually be found in Arkansas Code. It is Title 1, Chapter 4, Section 105, Pronunciation of state name. We're one of the few states to actually have a law about our pronunciation.
Which brings up the next point. There's an old rumor online that it's illegal to mispronounce the name of Arkansas and you can face steep fines (some even say jail time). Since the General Assembly had to meet to figure it out, it might be cruel to jail poor foreigners who visit Kansas and then come here. Searching the code, there is no evidence that it is illegal to mispronounce the name. However, the rumor comes from the fact that we have a "pronunciation" section in our code, and the wording: "the sounding of the terminal s" is an innovation to be discouraged."
It's discouraged, but you're probably not going to go to jail for it. We might laugh at you a little.
Little Rock's name is a little less interesting. Little Rock was actually named for a little rock. Early travelers used a stone outcropping on the bank of the Arkansas River as a landmark. "La Petite Roche" marked the transition from the flat Mississippi Delta region to the Ouachita Mountain foothills. Travelers would refer to the area as "the little rock" and the name stuck.
Arkansas is the "natural state" and our state motto is "regnat populus " (Latin for "the people rule").