borough (district), administrative and historic county of Kent, southeastern England. Its centre is the town of Gravesend, but it includes a section of the south bank of the River Thames above and below the town, and it runs inland to the crest of the chalk hills (North Downs) that traverse the county from west to east. The borough was once agricultural, with areas of orchards and market gardens, but has today become built-up and industrialized. Residential developments, factories, and chalk quarries have encroached extensively on the farmland. Area 38 square miles (99 square km). Pop. (2001) 95,703.