It is a cathedral town, and marketing and service centre for the surrounding farming country; Chelmsford's cattle market was established in about 1200. Following the construction of the Chelmsford and Blackwater Navigation (canal) in 1797 and the railway 46 years later, Chelmsford developed a significant industrial base. The main industries today are electronics, packaging, brewing, milling, and light engineering. The town's closeness to London means that it also acts as a residential suburb for commuters to the capital.
The site was first settled by the Romans, who in the first century AD built the town of Caesaromagus halfway between London and Colchester. The modern town grew from the medieval manors of Moulsham and Celmeresfort, which were linked at the beginning of the 12th century by a wooden bridge over the Chelmer. Many of Chelmsford's oldest buildings were torn down during the industrial-based expansion of the late 19th and early 20th centuries. One of the oldest remaining buildings is the Shire Hall, built in the Classical style by John Johnson in 1787. Johnson also helped to restore the 15th-century Church of St Mary, St Peter, and St Cedd, which has been Chelmsford's cathedral since 1951. A notable event in Chelmsford's history was the first ever wireless-telegraph broadcast, from the Marconi factory in February 1920.
The population of Chelmsford (1985 estimate) is 144,000.