Born at Acton, Canada West, Mann studied as a Methodist minister but worked in lumber camps in Parry Sound District and Michigan for eight years[4] before moving to Winnipeg, Manitoba, in 1879.

[5] During the 1880s he worked as a contractor for the Canadian Pacific Railway under James Ross and Herbert Samuel Holt, building sections of rail across the prairies and through the Rocky Mountains.

[5] While there, he was challenged to a duel by a Russian count, who later withdrew when Mann advised him that he would choose to use the broadaxe, claiming it to be Canada's national weapon.

[5] By 1895, the effects of the CPR monopoly on freight rates in Western Canada, together with its refusal to build branch lines into the northern prairie, prompted Clifford Sifton to offer federal bond guarantees to any other enterprise that wished to construct railways there.

[6] The CNoR would be the first railway to reach Edmonton, Alberta, and the full line was completed in 1915, upon the driving of the last spike in Basque, British Columbia.