 During the 20th century, the county became increasingly urbanised, particularly the southern part.To the existing county boroughs of Barrow-in-Furness, Blackburn, Bolton, Bootle, Burnley, Bury, Liverpool, Manchester, Oldham, Preston, Rochdale, Salford, St. Helens and Wigan were added Warrington (1900), Blackpool (1904) and Southport (1905).The county boroughs also had many boundary extensions.