This is going to be short but hopefully enough. Entirely an American creation. The first mention of Mrs Claus is from a short story from a Christian missionary named James Rees in 1849, "A Christmas Legend." The first time 'Mrs Claus' is named as such is by a Yale student in their magazine in 1851. However she didn't join widespread pop culture until the 1960s thanks to a successful children's book, How Mrs. Santa Claus Saved Christmas, by Phyllis McGinley. She has generally always been portrayed physically the same, and usually has red hair if not depicted white (most common hair colour to go white).

Edit: I can't believe I forgot to mention "Goody Santa Claus on a Sleigh Ride" by Katherine Lee Bates, the first real time she isn't just Santa's wife. That poem is where we got a lot of the physical descriptions and establishes her as her own person (albeit still a 'goody', a 'good housewife'). Since that came out in 1889 the image of her has remained largely unchanged.