Very little is known of Halpin's early life, though it is known that his background was in the building trade rather than in engineering. In 1800, he was made the Inspector of Works for the Dublin Ballast Board (the predecessor to the Commissioners of Irish Lights), succeeding Francis Tunstall. He was responsible for supervising the construction of new docks, bridges and other projects for Dublin Port.
One of these, the Bull Wall, along with associated projects, led to the creation of Bull Island in Dublin Bay, and enabled deep-draught ships to use the port for the first time. When the Ballast Board became responsible for lighthouses in 1810, George was appointed Inspector of Lighthouses as well as Inspector of Works. At that time there were only 14 lighthouses around the coast of Ireland.
Between 1810 and 1867 Irish lighthouses increased from fourteen to seventy-two under his direction. He established 53 new lighthouses, in addition to modernising a further 15: his projects included the Baily Lighthouse, the second Mew Island Lighthouse, and the Skelligs Lighthouse. He also set up the Irish lighthouse service's administration and management procedures, regularised employment of lighthouse keepers, and continued to oversee the development of Dublin's port.
A builder by trade, with no formal engineering qualifications, George designed and supervised the construction of over 50 lighthouses around the coast of Ireland in 57 years. Many of the great lighthouses of Ireland were designed by George including St. John’s Point in County Down, Rathlin West Light, the lighthouse cut into the cliff face in Rathlin island, the centuries old fort turned lighthouse in Valentia Island and Fanad Head.He also oversaw the modernisation of those original 14 lighthouses.
George Halpin died suddenly in July 1854 at the age of 75, while carrying out an inspection of a lighthouse. He was buried in Mount Jerome Cemetery, Dublin. He was succeeded as Inspector of Lighthouses by his son.