In April 1921 the county council voted to request a change of the county's name from Haddingtonshire to East Lothian. The government agreed and brought the change into effect as part of the East Lothian County Buildings Order Confirmation Act 1921, which received royal assent on 8 November 1921. The act also transferred ownership of the County Buildings to the county council. Shortly after the council took ownership of the building they extended it to the west by an additional block, designed by J M Dick Peddie & W J Walker Todd in a similar style, which was completed in 1932. Another extension adding a wing to the rear was completed in 1956.
