The Dublin and Kingstown Railway was the first railway in Ireland. It was opened to the public on December 17, 1834. It connected Westland Row in Dublin with the west Pier of Kingstown Harbour (Kingstown is now called Dun Laoghaire), about six miles. 

1837 map (extract): The environs of Dublin

Trial runs during the previous weeks had attracted hundreds of curious onlookers. They stood beside the recently constructed stone bridges that carried the newly laid iron rails on raised ground over the little streets at the back of Westland Row station.

Reference: Irish Times 14th December 2014 https://www.irishtimes.com/opinion/an-irishman-s-diary-on-the-dublin-to-kingstown-rail-line-1.2463456 (accessed 12Feb21)