Tower Mountain is the second highest peak in Ontario, only 14 meters lower than provincial highpoint Ishpatina Ridge, a full 700 km to the east. The peak is part of the range of hills on the northwest shore of Lake Superior, not far from the city of Thunder Bay. Two summits just south of the U.S. border in Minnesota (one of them Eagle Mountain) are just a bit higher, making Tower Mountain the third highest summit in the Lake Superior area.
The name "Tower Mountain" is relatively new. For many years this summit was just known as a unnamed spot elevation in the "Thunder Bay Hills". But the recent Ontario Base Map 1:20,000 GIS database clearly labels the summit with its name and new elevation.
The peak looks like a broad, flat-topped ridge, with surprisingly steep slopes (even some real cliffs) surrounding the central plateau. The summit is a very broad flat area, and it is marked by clearings with lots of debris from an old tower. You can see the tower footings, the wreckage of the wooden observation box, old cables, and electrical junk lying around. A rise to the north of the tower area may be the actual highpoint, but it’s hard to tell. There are no views, but if you bushwhack to the west for a tenth of a mile you will come to the top of the cliffs, where a nice vista of clear-cut forests extends for miles.
From Thunder Bay, drive west on TCH 11-17 to Kakabeka Falls, then turn left on Route 590. Follow that west and south to Route 588, and turn right (west). Stay on Route 588 for 28 km (17.3 miles), passing a junction with Route 593 and the one-building town of Suomi, until you reach a junction with an unsigned dirt road heading right (north) into the woods.
If coming from the USA, start in Grand Portage, Minnesota. Take Route 61 north for 5 miles to the Canadian border, cross into Canada, and a mile past the border turn left on Route 593, a paved wilderness road that winds for 30 miles (48 km) before ending at Route 588. Turn left, and after 11.7 miles (19 km) you will reach the junction with the dirt road heading north.
This road is a bit rough, climbing short, steep, bouldery hills in a couple places, but my guess is that most passenger cars will make it with just a few undercarriage scrapes. The road is not on any maps I know of. You want to follow it for 7.7 miles (12.35 km) from Route 588, through massive clear-cuts. The open terrain gives you a good view of Tower Mountain as you approach it—it looks impressive, a large prominent ridge with steep cliffs guarding its southwest slopes. The road goes almost to its base and turns right, and the best place to park is at about WGS84 -90.08512, 48.30457, just before the road starts a steep, rocky descent.
From here, bushwhack north-northwest up the slope—if you go too far west, you will encounter brushy cliffs, so it is best to stay right when in doubt. After a short, steep stretch you will gain the flatter terrain at the top of the ridge, where you head west-northwest towards the summit. There is no sign of the trail on the topo map (or any trail at all), but the bushwhacking is not too bad. A GPS is useful—the summit is at WGS84 -90.09444, 48.30801.