The earliest information about Mērsrags is from the 15th. century, when it was a small fishing hamlet beside the Gulf of Riga. There are many stories and myths about Mērsrags. Pirates, who lured ships ashore and plundered them, used to live here. During the ducal period, there was a large production of soap.
In 1842 a canal was dug from the north end of Lake Engure to the sea and in 1843 Mērsrags began to develop. In 1880 a lighthouse had been completed and the first ship was launched from the dockyard. Altogether 22 sailing ships were built in Mērsrags. Between 1860 and 1915 66 sailing ships were built in Upesgrīva village.
Until 1918 Mērsrags village and Upesgrīva village belonged to the parish of the Engure manor but in 1918 Mērsrags became a separate parish. Likewise in 1926 Upesgrīva became a separate parish.
In 1926 a narrow-gauge railway came to Mērsrags and in 1927 the port was built to satisfy the needs of fishing boats and shipping.
In the 60’s (20.th century) the development of the fish farm collective resulted in a great increase in the production of fish and canned products. The first block of flats and a distant steam heating plant were built. A new fish processing plant was constructed as well as a net repair shop and an engineering workshop. The village roads were repaired and asphalted
