Crerar had shown an early interest in railways as early as 3 February 1836 when he wrote a lengthy letter concerning a proposed railway between Halifax and Windsor. Later in 1836 the General Mining Association of London, England, owners of the Albion Mines, now Stellarton, decided to build a railway from the Albion Mines to its loading grounds on the East River. At that time there were few construction engineers in the area. Peter Crerar, a government land surveyor, was given the task. The plans were sent to the head office of the Mining Association in London, with the request that an engineer be sent out to execute them. When the plans were submitted to George Stephenson, builder of the locomotive who had engineered the construction of the Stockton and Darlington, England’s first railroad, he reported to the Mining Association that, in his opinion, the person who prepared the drawings was capable of executing them. The railway was then built under the supervision of Peter Crerar. Seven original maps and charts drawn by Crerar for the project between August 1837 and December 1838 were unearthed in a building being vacated by the Department of Mines in Stellarton. They are now preserved in the Nova Scotia Museum of Industry. The building of the Albion Mines Railway began in 1836 and the road was opened for traffic in 1839. The line, in length, was so nearly straight that the least radius of its curves was 1″ —. The estimated quantity of excavations was 400,000 cubic yards. At the water terminus there was a wharf long by wide, commanding a fall of above high water level at the shoots. The masonry, bridges, culverts, etc., were of cut freestone, from a nearby quarry. The total cost of construction was $160,000. While the railroad was being constructed, three locomotives were being built in England by Timothy Hackworth. They were landed at Pictou in May 1839 and brought up the East River in lighters, towed by a Mining Company steamship. The locomotives were Samson, Hercules, and John Buddle. The three locomotives were accompanied by John Stubbs, Hackworth's shop foreman, who directed their assembly before returning to England. Two locomotive engineers also came with the engines, George Greathead and George Davidson. Davidson served as Samson's driver throughout the engine's working life and accompanied the locomotive to railway exhibits in Chicago in 1883 and 1893. As George Patterson reports, the ceremonial opening in 1839 was celebrated province-wide: Herb MacDonald similarly recounts the celebrations: The Pictou Observer reported: Today the Albion Mines Railway is commemorated by the "Samson Trail" following the route of the old railway from the Nova Scotia Museum of Industry along the East River towards Abercrombie. The railway's locomotive Samson is preserved at the museum and is the oldest surviving locomotive in Canada.
Other engineering projects
Crerar's earliest recorded work was the drawing up plans for St. James' Anglican Church, Pictou in 1824. The main figure behind this church’s construction was Henry Hatton, later to be Crerar's son’s father-in-law. Throughout his life he served as a surveyor on roads and projects in the Pictou area, including the road between Mount Thom and Pictou, the Fisher's Grant Road, the French River, Huggins, and Sutherland Bridges, the pier at Arisaig, the Wallace Bridge, and the road from West Chester to Amherst. In 1845 he was a member of a local committee in Pictou County formed to support the proposed Halifax and Quebec Railway project. In 1851, as part of the first phase of planning for the Nova Scotia Railway, he carried out surveys for a proposed route north from Truro to Pictou. When built, the "Pictou Branch" followed another route selected by Sandford Fleming. Crerar served as Deputy Registrar General of Pictou County. He was later made Commissioner for Improvements to the Pictou section of the Main Post Road of Pictou.
His only known residence in Scotland was the farm of Cuiltrannich, in Lawers, Kenmore Parish, on the north shore of Loch Tay. His family departed for Nova Scotia in July 1817, probably aboard the Brig Hope, which sailed from Greenock to Pictou in 1817. He first gained employment as a schoolteacher.
Family
His wife was Anne Clarke, daughter of Ewan Clarke. Peter and Anne had eight children: John Crerar ; May Crerar ; Captain Ewan Clarke Crerar ; Capt. William Grant Crerar ; Dr. James Peter Crerar ; Capt. Daniel Crerar ; Capt. Peter Crerar ; Capt. David Stewart Crerar.
Death
His Pictou obituary reads as follows: Died... At Pictou, on Wednesday, 5th inst., Peter Crerar, Esq., a native of Breadalbane, Perthshire, Scotland, First Deputy Surveyor and Registrar of Deeds for the County of Pictou, aged 71. But few men have passed from our midst whose loss will be more generally or so extensively regretted. He has left a widow and seven sons to mourn their loss. His catholic spirit, his clear judgment, and his honest disposition, made him one of the most respected members of the community, as was evinced by one of the largest funeral processions ever witnessed at that place. He was connected with the Church of Scotland from his youth, and clung to her standards through all her trials and difficulties, and was Chairman of St. Andrew’s Church for many years previous to his death, in which capacity he made entire satisfaction. Among his last expressions were these words, "I have unwavering confidence in Christ Jesus my Saviour." He is buried in the Laurel Hill Cemetery, Pictou.
