Here is a map to show how wrong FB are:
Kendal was the administrative county town of the county of Westmorland from 1888 to 1974. It was listed in the Domesday book as being part of Yorkshire but the historic county of Westmorland had a vast swathe of England and indeed Scotland contained in it.
In 1974 the county of Cumbria was officially created to replace Westmorland and did incorporate a bit of Lancashire that was on the northern side of Morecombe Bay in the Furness area. A group of activists is currently going round replacing Cumbria signs with Westmorland and Lancashire ones on the original boundary.
It is isn't only Facebook that have a problem with Cumbria, I registered on a Montessori website for a competition and they didn't even have the county listed! So if you are passionate about getting the facts right then sign up to the Facebook group and help get the town of Kendal located in the correct county!