The Royal Family used the Deeside Line for travel to and from Balmoral Castle and when they were in residence a daily special 'Messenger Train' ran from Aberdeen; for most of the railway's life this was its only Sunday service.

[13] The railway opened short of rolling stock as only half of the twelve locomotives and twenty-four of forty passenger carriages ordered had arrived.

[15] The inquiry found that the driver, attempting to make up time after a late start, had over-run previous stations and been approaching the terminus with excessive speed.

[21] The route between Nairn and Keith authorised on 21 July 1856 required less earthwork, reducing cost, but had steeper gradients than had originally been proposed, and the Great North contributed £40,000 towards a bridge over the Spey.

[27] Plans to reach fishing ports at Macduff and Banff from Inverurie were proposed when the Great North was first suggested, but failed because of the lack of financial support.

[35] The Great North sought to have its own route west of Keith, with Grantown-on-Spey as an objective, where it hoped to meet any possible line between Perth and Inverness.

[27] With promises of substantial goods traffic of iron and timber and from the local whisky distilleries,[42] extension of the line to Dufftown into Strathspey was sought and obtained on 17 May 1861.

The 32+1⁄2-mile (52.3 km) line first headed north to meet an extension of the Morayshire Railway at Strathspey Junction (called Craigellachie from 1864), before following the River Spey to Abernethy.

The railways met 3 miles (4.8 km) north of Boat and conflict arose over the manning of the signalbox at the junction, with the Highland refusing to make any contribution.

The Morayshire extension and the Strathspey both opened on 1 July 1863 and the Great North provided a service of four trains a day over the line, which gave an alternative route between Keith and Elgin.

[45] On 30 July 1866 permission was given to the Morayshire and Great North to amalgamate with agreement, and the loss-making services between Orton and Rothes were withdrawn without notice the following day.

[61] The Limpet Mill Scheme was a line presented in an 1862 bill by the nominally independent Scottish Northern Junction Railway, but supported by the SNER.

Despite local opposition, the route was approved by parliament in 1863, but was revoked the following year when the SNER obtained permission for a railway through the Denburn Valley.

[67] Interest in the line was restored after Prince Albert purchased Balmoral Castle, to which the Royal Family made their first visit in 1848, and the Aberdeen Railway was able to sell its shares.

The railway was now paying a dividend and seeing increased traffic, but rolling stock, track, signals and stations all needed replacing in a project that was to cost £250,000 (equivalent to £32,110,000 in 2023).

[98] On 27 November 1882 Inverythan Bridge on the Macduff Branch near Auchterless collapsed as a locomotive hauling five goods wagons, a brake van and four carriages crossed.

[104] The Great North had opened using a system of telegraphic train orders, and as the signalling was being upgraded this was being replaced with electric tablet working over the single line sections.

The Highland Railway route was chosen, but the Great North won a concession that goods and passengers that could be exchanged at any junction with through bookings and with services conveniently arranged.

[113] With no judgement by 1897, the Great North prepared to apply again for running powers over the Highland to Inverness, this time agreeing to double track the line, but the commissioners published their finding before the bill was submitted to parliament.

Suburban services were also introduced between Aberdeen and Culter on the Deeside Line in 1894, after the track had been doubled, starting with ten down and nine up trains calling at seven stops in twenty-two minutes.

Encouraged by its success, the company obtained permission in 1893 to build an hotel and golf course at Cruden Bay, about 20 miles (32 km) north of Aberdeen.

The 17-mile (27 km) long Aberdeenshire Light Railway was independently promoted in 1896 to serve Skene and Echt, with tracks laid along the public roads in Aberdeen.

[124] A light railway was proposed to cover the 4+1⁄2 miles (7.2 km) from Fraserburgh to Rosehearty, but the scheme was abandoned after opposition to laying tracks on the public road.

[137] Aberdeen joint station was congested, resulting in delayed trains, and the low, open platforms were frequently covered in oily slime due to the large quantities of fish that passed through.

[146] Afterwards the economic situation deteriorated and the railway companies advised the trade unions in 1928 that wages would need to be cut; this was implemented in August 1930 after the Wall Street Crash the previous year.

[149] Optimism returned and traffic increased after 1933, and a luxury rail land cruise, the "Northern Belle", ran over former Great North lines.

[174] They were all fitted with Clark's patent smoke preventing system that improved fuel economy[175] and painted green with black borders, and red buffer beams.

[176] John Folds Ruthven replaced Clark in 1855 and an order was placed with Beyer, Peacock & Co. for two 0-4-0 tank engines[n] to bank trains on the line to Waterloo near Aberdeen harbour.

[214] Later, shorter six-wheeled and bogie compartment carriages were built for secondary services, and communication cords and steam heating were fitted in the early years of the twentieth century.

The cars were introduced on the Lossiemouth branch and the St Combs Light Railway, but when in motion there was considerable vibration that was uncomfortable for the passengers and caused problems for the steam engine.