On the 1st April 1911, Eastbourne became a County Borough with a population of 52,542, but further development was brought to a standstill by the outbreak of World War 1 in August 1914. In that year, however, the Corporation agreed to contribute £3,960 towards the support of an orchestra to provide good music throughout the year. During the war years the Corporation Transport Depot manufactured munitions, and in 1917/18 buses were driven by gas because of the petrol shortage. By the 11th November 1918 although Eastbourne remained unscarred, 1,065 of her townsfolk had given their lives for their country.

Immediately after the war a Council Housing Scheme was commenced, and unemployed were absorbed in work on creative schemes which included the Redoubt Gardens, Holywell, tennis courts and hospitals. Eastbourne Publicity Department came into being, and the town's various amenities were published more effectively. In 1922 bathing, bands and buses on Sunday were matters of considerable controversy, but a poll favoured the three 'B's, popularly so called, which then became the normal life of the town. By now the population had reached 62,030.

In 1924 the Towner Art Gallery, one of the finest on the South Coast, was established in an old Manor House in the Old Town through the generosity of J. C. Towner, a former member of the Town Council, who had bequeathed £6,000 and twenty pictures for its foundation. In 1925/26 the Town Council, viewing with alarm the indiscriminate building, taking place in various parts of the countryside, promoted a Bill to preserve 4,100 acres of downlands, including Beachy Head at a cost of £91,290.

Today the Corporation farms part the vast, unspoiled area that provides a perfect background for this beautiful resort, which nestles in the shoulders of the South Downs. It is recorded that six conferences met in Eastbourne in 1928, forerunners of the very many which now meet in this southern Conference Resort each year. By 1929 the volume of summer coach traffic had so increased that the Central Motor Coach Station was planned. In 1931 a new bandstand was built at the Redoubt at a cost of nearly £10,000. About that time it was decided to open the town bowling greens, tennis courts and putting greens after 2:30 pm on Sundays. The present Grand Parade Band Arena was completed in 1935 to seat 3,500 people, at a cost of £29,000 compared with £350 raised by public subscription nearly forty-nine years previously. On the same day Helen Gardens at the foot of Beachy Head was opened. In that year Southern Railway electric train service to Eastbourne was inaugurated by the Lord Mayor of London. A new Police Headquarters was opened in 1938 at a cost of £49,433.

Upon the outbreak of World War 11 in 1939 Eastbourne received 17,000 children and hospital patients to its homes, mainly from the London area. A year later the German air force commenced hit and run attacks on the South coast and Eastbourne became an evacuated area, the population dropping suddenly by almost 40,000. Nearly 700 high explosive and 4,000 incendiary bombs fell on the town, 172 townspeople were killed and over 900 injured, 475 houses were destroyed and 11,000 damaged. The world famous Carpet Gardens on Grand Parade were producing onions. Royal Naval, Army and R.A.F. personnel filled the hotels. When hostilities ceased in 1945 Eastbourne faced a tremendous task of recovery.