You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Lancashire

Context:
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 Blackpool (1904), Southport (1905), and Warrington (1900). The county boroughs also had many boundary extensions. The borders around the Manchester area were particularly complicated, with narrow protrusions of the administrative county between the county boroughs – Lees urban district formed a detached part of the administrative county, between Oldham county borough and the West Riding of Yorkshire.

Question:
When was Warrington added to Lancashire?

1900