In the 19th century, Muar became the most important town in Johor after Johor Bahru. This situation influenced the development of the town of Muar in political, economic, and social aspects during the specified period, which was under the rule of the Sultanate of Johor and subsequently the British. Therefore, this article aims to examine the extent of the development of Muar town, Johor, from 1884 to 1940 in supporting the claim that this town was the most important during the specified period. The research has outlined several objectives, including identifying the administrative structure of the Muar district, reviewing the economic activities in the Muar district, and analyzing social developments in the Muar district during the focus period of this research. To achieve the stated objectives, this research utilizes qualitative methods and entirely adopts a historical research approach. The materials and sources are obtained from the National Archives of Malaysia, the Johor Branch of the National Archives of Malaysia, the Muar District Office, the Johor Public Library Corporation, and the National Library of Malaysia. The research results indeed show that Muar was the most important town in Johor from 1884 to 1940. This situation is also seen as the reason for Muar town being elevated to the Royal Town of Johor, a status conferred by Sultan Johor, Sultan Ibrahim ibni Almarhum Sultan Iskandar, on 5th February 2012.