The line was initially considered in 1831 as a way to bring the products from the burgeoning area around Peterborough to markets on Lake Ontario through the port in the town of Cobourg.

A series of companies took over operations of the C&PRy, including a lease to the shareholders of the Port Hope, Lindsay & Beaverton Railway, who ran a competing line only a few miles away.

The southern portion of the line, below Rice Lake, had a second life from 1867 as part of the Cobourg, Peterborough & Marmora Railway & Mining Company.

This was a network using the original C&P, a short run known as the Blairton Extension, and the Trent River between the two which was used to ship iron ore from the mines at Marmora to market.

James Gray Bethune arrived in Cobourg in 1816 and started several enterprises before settling on running a combined general store and post office.

By the late 1820s it was becoming clear that Peterborough was going to be a success, and there was a definite need to provide markets for the burgeoning lumber mills and farms springing up in the area.

Bethune's steamer network was hampered by the lack of any ability to reach Lake Ontario, a problem for any of the ports in the area.

While Bethune was busy setting up the locks, he was also engaged with local businessmen in an effort to build a railway from the Sully dockyard to the port in Cobourg.

In 1832, Rubidge returned a proposed route running through several valleys from D'Arcy Street in Cobourg northward to the docks at Sully.

[4] On 6 March 1834 the Cobourg Rail Road Company was chartered to build the line within set times, and given an initial grant of £10,000 to start the work.

Additionally, in 1833 the provincial government hired Nicol Hugh Baird to examine the Trent River with hopes for opening it for navigation.

[3] With the railway line abandoned, the town again hired Baird in 1842 to survey the route for a plank road to Rice Lake.

[7] Luckily for Cobourg business interests, the Port Hope efforts had failed, and competition to the plank road had never materialized.

[9] Financial problems arose in 1854 with the advent of the Crimean War which created a labour shortage and wages rose to one dollar per twelve-hour day.

[4] However, to save money, Zimmerman did not fill in the pilings along the northern sections of the bridge, which were noticed in the spring of 1854 to have shifted due to ice.

[4] John Fowler was brought in to replace Spaulding, and the bridge was gradually upgraded, starting with the construction of causeways in the shallower portions.

By the summer of 1859 four miles had been completed from the east side of the Otonabee River across a bridge built between 1867 and 1871, where it crossed the Midland Railway of Canada's branch to Lakefield.

The shareholders rejected Covert's plan, and instead handed it to John Henry Dumble, who had some experience from the Grand Trunk Railway (GTR).

[16] A major threat to the operations was the construction of a spur from the competing Port Hope, Lindsay and Beaverton Railway (PHL&B), which had started pushing towards Peterborough and reached it on 12 May 1858.

In order to ward off this upcoming threat, Dumble arranged contracts with a number of lumber interests in the town to continue using the C&PRy.

He agreed, only to find the next day that the line had not been leased to the GTR, but the shareholders of the Millbrook Branch - Boulton, Covert and Fowler.

Some time in 1861 they moved the locomotives to their own yards in Port Hope, and then sabotaged the bridge by removing iron bolts and fittings, taking them for use on the Millbrook line.

[17] During a town meeting in 1864, Dumble revealed the successful trickery and sabotage, but offered an optimistic note that the C&PRy still had a shorter route than the Port Hope line, and ended at a better harbour.

A new plan to service the mines was brought up by W. W. Dean at the 1864 meeting, and in 1865 John Dumble was asked to examine the concept of selling the line to investors for hauling iron.

The final haul ended on an inclined ramp on the docks in Cobourg, where they ore was again dumped into barges or steamers, typically bound for Rochester.

The residual capital of the original CP&M&M was sold off to the Cobourg, Blairton & Marmora Railway and Mining Company, formed on 23 June 1887.

Their interest was primarily in an attempt to connect the Blairton section to the Ontario and Quebec Railway which passed between the two ends of this branch.

This was ultimately unsuccessful, and by this time several other lines, notably the Central Ontario Railway which ran directly through the Marmora mines, were providing service in this area.

It ran to a point just north of the current Ontario Highway 401 where it turned northeast in a series of curves between Precious Corners and Baltimore.

From Hiawatha the line ran roughly northward towards Peterborough, arriving in Ashburnham, on the east side of the Otonabee River.