The so-called "cold cases" include ones dating back to the founding of the force in 1974.
Det Supt Simon Atkinson, from the Homicide and Major Inquiry team, said the money would be used to employ 35 new staff.
The funding comes from the office of the West Yorkshire Police and Crime Commissioner.
Det Supt Atkinson said: "One undetected murder is one too many.
"That is why the PCC has announced these extra resources to recruit staff to review all these cases and we are determined to do our best to get some answers, to find the people responsible and to bring them to justice."
He said major advances in forensic techniques could make a real difference in reviewing all 55 cases.
West Yorkshire's most well-known unsolved murder cases include the death of 13-year-old Lindsay Rimer, from Hebden Bridge, in 1995.
Her body was found in the Rochdale Canal five months after she disappeared.
Lindsay's sister, Kate Rimer, said: "We miss her so much and every memory of her is tainted because of what happened to her."
Police and Crime Commissioner Mark Burns-Williamson said: "There are still people out there, in our communities, enjoying their liberty, who are responsible for terrible crimes.
"They present a real threat of further harm and need bringing to justice."
Mr Burns-Williamson said the money had been found from spending reviews and would fund the team for 18 months.
Funding of £1.5m will be used to help West Yorkshire Police review 55 unsolved murders.