The northern section of the county, today known as Fingal, varies enormously in character, from densely populated suburban towns of the city's commuter belt to flat, fertile plains, which are some of the country's largest horticultural and agricultural hubs.

The Vikings raided across Ireland, Britain, France and Spain during this period and under their rule Dublin developed into the largest slave market in Western Europe.

They evaded the intercepting army of High King Ruaidrí Ua Conchobair by marching through the Wicklow Mountains, arriving outside the walls of Dublin in late September.

In 1901, The Irish Times reported that the disease and mortality rates in Calcutta during the 1897 bubonic plague outbreak compared "favourably with those of Dublin at the present moment".

[22] Most of the upper and middle class residents of Dublin had moved to wealthier suburbs, and the grand Georgian homes of the 1700s were converted en masse into tenement slums.

[25] Unlike their counterparts in the north, "southern unionists" were a clear minority in the rest of Ireland, and as such were much more willing to co-operate with the Irish Parliamentary Party (IPP) to avoid partition.

[26] The question of Home Rule was put on hold due to the outbreak of the First World War but was never to be revisited as a series of missteps by the British government, such as executing the leaders of the 1916 Easter Rising and the Conscription Crisis of 1918, fuelled the Irish revolutionary period.

The Liffey, at 132 kilometres (82 mi) in length, is the 8th longest river in Ireland, and rises near Tonduff in County Wicklow, reaching the Irish Sea at the Dublin Docklands.

[35] The bedrock geology of Dublin consists primarily of Lower Carboniferous limestone, which underlies about two thirds of the entire county, stretching from Skerries to Booterstown.

As a temperate coastal county, snow is relatively uncommon in lowland areas; however, Dublin is particularly vulnerable to heavy snowfall on rare occasions where cold, dry easterly winds dominate during the winter.

[40] During the late summer and early autumn, Dublin can experience Atlantic storms, which bring strong winds and torrential rain to Ireland.

[44] While baronies continue to be officially defined units, they ceased to have any administrative function following the Local Government Act 1898, and any changes to county boundaries after the mid-19th century are not reflected in their extent.

However, results from the 2022 census revealed that immigrants from non-EU/UK countries were the largest source of foreign-born residents for the first time, accounting for 12.9 percent of the county's population.

[98] The influx of Indians is driven in part by multinational tech companies such as Microsoft, Google and Meta who have located their European headquarters within the county, in areas such as the Silicon Docks and Sandyford.

[121][122] The Luas and rail network regularly experience significant overcrowding and delays during peak hours, and in 2019 Iarnród Éireann was widely ridiculed for asking commuters to "stagger morning journeys" to alleviate the problem.

[124] Due to the county's small area and high degree of urbanisation, there is a preference for "D" registered used cars throughout Ireland, as they are considered to have undergone less wear and tear.

[130] As Ireland's most populous county, Dublin has the highest total household income in the country, at an estimated €46.8 billion in 2017 – higher than the Border, Midlands, West and South-East regions combined.

In Dublin (both city and county), residents will commonly refer to themselves as a "Northsider" or a "Southsider", and the division is often caricatured in Irish comedy, media and literature, for example Ross O'Carroll-Kelly and Damo and Ivor.

Many firms, including Barclays and Bank of America, pre-emptively moved some of their operations from London to Dublin in anticipation of restricted EU market access.

[139] A survey conducted by Ernst & Young in 2021 found that Dublin was the most popular destination for firms in the UK considering relocating to the EU, ahead of Luxembourg and Frankfurt.

[145] As a result of Dublin city's location within a sheltered bay at the mouth of a navigable river, shipping has been a key industry in the county since medieval times.

Due to the growth of Dublin city and its commuter towns in the north of the county, the region is considered to be under significant pressure from urban sprawl.

In the absence of increased private planting, the county's commercial timber capacity is expected to decrease in the coming decades, as Coillte intends to convert much of their holdings in the Dublin Mountains into non-commercial mixed forests.

Numerous Irish and multinational food and drink companies are either based in Dublin or have facilities within the county, including Mondelez, Coca-Cola, Mars, Diageo, Kellogg's, Danone, Ornua, Pernod Ricard and Glanbia.

The First Dáil of the revolutionary Irish Republic met in the Round Room of the Mansion House, the present-day residence of the Lord Mayor of Dublin, in January 1919.

Following independence, the lodge was earmarked as the potential home of the Governor-General, but this was highly controversial as it symbolised continued British rule over Ireland, so it was left empty for many years.

Once the centuries-long seat of the British government's administration in Ireland, Dublin Castle is now only used for ceremonial purposes, such as policy launches, hosting of State visits, and the inauguration of the president.

[177] Dublin is among the most socially liberal places in Ireland, and popular sentiment on issues such as LGBT rights, abortion and divorce has often foreran the rest of the island.

In general, the south-eastern coastal regions of the county such as Dún Laoghaire and Dublin Bay South are a stronghold for the liberal-conservative Fine Gael party.

Although a small county in size, Dublin contains one third of Leinster's 168 golf courses,[194] and three-time major winner Pádraig Harrington is from Rathfarnham.