Sentence:  Old attitudes are held more tenaciously in the Tidewater than the Piedmont ; so that a line running down the length of the South marking the upper limits of <WSD>tidewater</WSD> would roughly divide the Old South from the new , but with , of course , important minority enclaves . 
Meaning of the word marked with <WSD> tags:  low-lying coastal land drained by tidal streams