Sentence:  Old attitudes are held more tenaciously in the Tidewater than the Piedmont ; so that a <WSD>line</WSD> running down the length of the South marking the upper limits of tidewater would roughly divide the Old South from the new , but with , of course , important minority enclaves . 
Meaning of the word marked with <WSD> tags:  a spatial location defined by a real or imaginary unidimensional extent