Original: Two other major arteries are also sometimes identified as the northern border of "lower" or "downtown Manhattan": Canal Street, roughly half a mile north of Chambers Street, and 23rd Street, roughly half a mile north of 14th Street.
Simplified: Two other major arteries are also sometimes identified as lower Manhattan's northern border: Canal Street, half a mile north of Chambers Street, and 23rd Street, half a mile north of 14th Street.