It was formed in 1970, after the amalgamation of the cities of Port Arthur and Fort William and their respective transit agencies.

Compounding the matter was the Canadian Pacific Railway's decision to build its grain elevators and rail yards in neighbouring Fort William, 6 km (4 mi) away.

[11] In 1891, the town of Port Arthur was authorized to construct and operate the first municipally owned street railway in Canada.

Instead, McDonald and Company commenced operations of a private omnibus, connecting the Port Arthur Street Railway's southern terminus at Fort William's northern town limits into the downtown core of Fort William.

On June 1 of that year, service was extended to Prudence Street, which was the northernmost point of Fort William at the time.

By the end September, the route extended all the way to Westfort,[14] a community that supported Port Arthur's initiative to build a streetcar line.

[15] This original streetcar line, primarily on Fort William Road, resembles today's #1 Mainline bus route.

[16] The Port Arthur Public Utilities Commission which ran the street railway acquired its first 36-passenger bus (painted maroon and cream) in August 1946 manufactured at the Canadian Car and Foundry plant in Fort William.

The trolley buses were manufactured by J. G. Brill and Company at the Canadian Car and Foundry plant in Fort William.

One would have to transfer buses at a loop east of the Canadian Lakehead Exhibition grounds, at the Fort William city limits.

The Crosstown route connects Westfort and downtown Port Arthur, allowing riders to enjoy a shorter ride between the city's distant ends (saving 15 minutes).

Exact cash fare on Thunder Bay Transit is $3.25, support persons ride free, as do children under the age of twelve.

A transfer pass can be obtained when boarding with cash or tickets, and allows passengers to change buses up to two times for the price of one fare.

[22] Students at Lakehead University and Confederation College receive a U-Pass as part of their tuition, which allows for unlimited trips during the school year for the person to whom the pass is issued.

17 Current River City Hall: 18 Westfort 45m (Other off-peak times) 5 Edward 30m (Saturdays and Summer) 5 Edward or 16 Balmoral 45m (Other off-peak times) 3M Memorial 3M Memorial 3M Memorial 3C County Park or 3J Jumbo Gardens City Hall: 10 Northwood or 14 Arthur 3C County Park City Hall: 10 Northwood 45m (Late evening) (Westfort) 6 Mission Select Runs (Westfort) 2 Crosstown (Westfort) 2 Crosstown 4 Neebing Select Runs 11 John 13 John-Jumbo 9 Junot (Limited) 14 Arthur 8 James (Limited) or Lakehead University (Short Turn outside mall hours) 3M Memorial 3M Memorial 7 Hudson 30m 16 Balmoral 30m 7 Hudson 45m 3M Memorial 8 James 12 East End 2 Crosstown 1 Mainline 1 Mainline Note: Routes with availability stating “All week” indicate service is always available during service hours.

route connects the Fort William First Nation reserve on the opposite side of the Kaministiquia River to the city's Westfort ward.

[27] Thunder Bay Transit owns a fleet of 48 buses, which consists of all Nova Bus LFSs.

[35] These electronic signs are located at the Thunder Bay Regional Health Sciences Centre, Lakehead University, Confederation College, Intercity Shopping Centre, and Thunder Bay Transit's two downtown transit terminals, with a seventh sign planned for the Westfort neighbourhood in the city's south end.

[21] A test of the system was released on March 17, 2008, and allowed passengers to view arrival times for routes 2 Crosstown, 3 Northwood, 8 James and 9 Junot.

[36] To accommodate disabled passengers, Thunder Bay Transit buses are wheelchair accessible low-floor models.

[32] Low-floor buses are capable of kneeling to street level and have extending ramps which allow wheelchairs to board safely.

Thunder Bay Transit buses had 19,175 rides by persons in wheelchairs in 2006, the most per capita in Ontario.

Thunder Bay Transit operates two bus terminals in the north and south cores of the city.

In addition, three points of interests are major transit hubs in the city: Lakehead University, Confederation College, and Intercity Shopping Centre.