Portsmouth sits on US 23 in southernmost Ohio, almost on the Kentucky border. Columbus is about 95 miles north (under two hours by car) and Cincinnati 100 miles west. There is no commercial air service; the nearest airports are Columbus (CMH) and Cincinnati-Northern Kentucky (CVG), each roughly two hours away.
Greyhound buses serve the city from both Columbus and Cincinnati. Driving in is straightforward and parking in the downtown core is plentiful and largely free.