George Frederick Arthur Grimes was born on 29 June, 1877 at Channel, Newfoundland, the son of William and Amelia (White) Grimes. His father was a member of the Newfoundland Constabulary and served in several outports. George received his early education at the Brigus Public School and at age 13 years entered the St. John's dry goods firm of David Sclater. In 1900 he married Annie Clarke and they had seven daughters. Two years later he joined the city firm of George Knowling Ltd. In 1912 Grimes became manager of the Dry Goods Department of the Fishermen's Union Trading Company where he remained until 1922 when he started his own business. During the 1920s he was Secretary-Treasurer of the Supreme Council of the Fishermen's Protective Union (FPU). He was also a member of the Oddfellow and Mason Societies, secretary of the East End United Church School Board, and a president of the M.C.L.I. Debating Club.

Although William Coaker, the founder in 1908 of the FPU, was himself not a socialist, Grimes was. It was his criticism of the Newfoundland economic system, his support for the St. John's labour movement, and his business experience, which brought him to Coaker's attention. A Methodist lay teacher, Grimes was one of a small group of local residents in St. John's who in 1906 formed a socialist society to debate the weaknesses of the capitalist system. This group survived for a decade; one of its most famous students was a future premier of Newfoundland, Joseph R. Smallwood, who received his first exposure to socialist literature from him. In 1908 Grimes was the Financial Secretary of the recently formed St. John's Trades and Labour Council. When the Newfoundland Industrial Workers' Association was established in 1917 by city labourers, Grimes was a prominent speaker at its meetings and served on its co-operatives committee.

In 1913 Grimes was one of 8 FPU members elected to the House of Assembly to form the Opposition along with Sir Robert Bond's Liberals. He won the District of Port de Grave by a majority of 174 votes, but in 1919 lost it to Sir John Crosbie. In 1923 Grimes returned to the House as the representative for Fogo, while in the 1924 and 1928 elections he was elected for Twillingate and Lewisporte respectively. In the House of Assembly Grimes was a prohibitionist, and an advocate of female suffrage, which was legislated in 1925. On labour issues, for instance, he favoured a public financial relief program for widows, an arbitration system to settle wage disputes, and a minimum wage. His efforts to effect reform in the fishery, after his appointment in 1923 as Minister of Marine and Fisheries, were unsuccessful because of the defeat in the House of William Warren's Administration the following year. After his re-election in 1928 as a member of Sir Richard Squires' Liberal Party, Grimes received the Deputy Speakership of the House of Assembly. He died at St. John's on August 1O, 1929. In the Fishermen's Advocate on 16 August, Coaker wrote that Grimes "consistently lived up to the pledge of 1913 to serve country first" and his "example may well be followed by those whose duty it is to serve their country and countrymen."