Businessman and politician. Dalglish was born in Glasgow, the son of a Lord Provost of the city. He was educated at the University of Glasgow, before starting work in the family calico printing firm, R. Dalglish, Falconer & Co, based in Lennoxtown.
Dalglish was elected as an Independent Radical Member of Parliament for Glasgow in 1857 and, proving to be a popular representative, was successfully re-elected in 1859, 1865 and 1868, before retiring in 1874. He was noted for his fine hospitality at his home, Kilmardinny House in Bearsden, which he had bought in 1853.
He was prominent in the erection of Marochetti's statue of the Duke of Wellington in front of the Royal Exchange Square in Glasgow and is, himself, remembered through a bas-relief on Queen Victoria's statue in George Square.