Samuel "Sam" Dullard moved to Ocean Shores, California from Hutchinson, Kansas (ref: S01E20A, "Snow Day").
Otto, Twister, and Reggie address him as "Squid", a term developed on motorcycle tracks in Southern California. Squid comes from the term "squirrelly" and was given to new riders who exhibited an unpredictable and unsteady riding style on account of them being new to the sport.
The new kid on the block, he is introduced to us on the first episode, where he and his divorced mother Paula moved to the only vacant house in the cul-de-sac.
A very smart and intelligent kid, Sam is the same age as Otto and Twister, but was promoted one grade up at school ("mom's idea") and is in Reggie's class. He is the voice of conscience and common sense for the group: his fears and his intelligent analysis usually keep the other kids out of serious danger. He is very good at math and science, and is also a very literate computer user who has developed applications. He is rarely seen without his trusty laptop computer, which he carries along everywhere he goes.
It was never explained why the Dullards moved from Kansas to Ocean Shores. Over the years, some fans offered the theory that the move might have had to do with Sam's asthma and allergies: living in a state where every year the boy would have been exposed to a lot of pollen, his condition would have worsened periodically, which would have a negative impact on his quality of life.
In California, away from the prairies and exposed to the salty air coming from the sea, Sam would probably be more protected from his allergies and his asthma, though it was shown in at least one episode ("Big Air") that his condition could still get out of control.