It opened in stages from 1888, being extended to Neilston and Newton, giving the Caledonian Railway a fully independent route by 1904.

The Caledonian Railway hoped to develop suburban traffic in south Glasgow where the new line passed through those districts, but street tramcars limited the success of this.

The eastern section from Neilston and Newton to the Cathcart circle lines developed as outer suburban railways, and were electrified in the 1960s.

Moreover, the towns in the area, including Saltcoats and Stevenston, as well as Irvine, were of growing importance for industrial activity and serving them would bring further passenger and goods revenue.

The Earl of Eglinton was the owner of Ardrossan Harbour and wished to encourage any initiative that would enhance the value of his property, and he lent his support to the scheme.

Encouraged by this, the company presented a bill in the 1884 session for a much more ambitious scheme, dropping the junction with the G&SWR and making lines to Ardrossan itself, and to Irvine and Kilbirnie; this was passed as the Lanarkshire and Ayrshire Railway Act 1884 (47 & 48 Vict.

c. lxxxvii) was obtained in 1885 authorising substantial subscription in the scheme by the Caledonian Railway, which was in any case going to work the line.

The Caledonian also committed itself to long term carriage contracts with mineral forwarders, relying on the new line.

[1][2][3] The G&SWR was alarmed by this intended incursion into its territory and quoted cheap rates for coal from Hamilton and Bothwell; it had running powers over the North British Railway lines there; however its longer mileage and the toll charges to the NBR made it impossible to sustain the cheap rates and the scheme was dropped after six months.

[2] Although Kilbirnie was a significant town, with a population of 3,405, the dominant feature of the branch was the ironworks at Glengarnock (and also a chemical works there), situated on the west side of the G&SWR main line.

This immediately ignited bitter competition for the passenger traffic between Glasgow and the Clyde islands and to Belfast, with some very fast through journeys being timetabled.

Such a line would have been a coup in the battle against the rival G&SWR, but a more balanced view prevailed: the line would have cost £440,000 and would have been subject to an immediate price war, frustrating any likelihood of great profits and the construction would have exhausted the Caledonian's fund of capital for major works, for which the priority lay elsewhere.

[1][2] The petition from Ayr urged an extension south and west but the Caledonian and the L&AR were more interested in extending east and north.

The L&AR had been successful in capturing the majority of the mineral traffic from Lanarkshire to Ardrossan, but it still required the heavy and slow trains to travel via the junctions on the south side of Glasgow, along congested routes.

Part of the haul was along the Glasgow Barrhead and Kilmarnock joint line, shared with the GS&WR, which had difficult gradients, incurring significant extra engine power costs.

The Cathcart to Newton section was opened on 6 January 1904: now the Caledonian had a fully independent route from Lanarkshire to Ardrossan.

This section has become two suburban branch lines, from Newton to Glasgow Central via Kirkhill (alternating between the Maxwell Park and Mount Florida sides of the Cathcart Circle), and from Neilston to Glasgow Central via the Mount Florida side of the Cathcart Circle.

The arrangement of the passenger platforms at Cathcart is such that the Maxwell Park to Newton trains pass behind them but cannot make a station call.

[7] Some landmarks of the railway still exist throughout the former route: a large viaduct remains to the north of Kilwinning, now used as part of the National Cycle Network.

[5] Local passenger trains between Uplawmoor and Ardrossan were withdrawn from 4 July 1932 and stations Lugton to Saltcoats closed.

These offered a return journey from Glasgow to Stevenston, Saltcoats or Ardrossan for half the single fare; the stations were specially made available for the excursions; they proved extremely popular and were repeated in 1934.

At Clarkston West Junction, the subsequent location of Williamwood station, a facing connection towards Clarkston on the East Kilbride line (the former Busby Railway) diverged; this was installed to give and alternative route for mineral trains from the Bothwell area towards Ardrossan and was opened in 1903.

Such a line would have simply duplicated the existing connection to Lugton East Junction, and in 1930 use of the L&AR was declining steeply.