Green’s Dictionary of Slang

(US) fundamental, conservative.

1896		H. Frederic Damnation of Theron Ware 53: He’s all wool an’ a yard wide when it comes to right-down hard-pan religion [DA].
1907		R. Service ‘The Little Old Log Cabin’ in Songs of a Sourdough 57: When a man gits on his uppers in a hard-pan sort of town.