The birth of Trelew is closely linked to the history of Welsh colonization. It was the result of a great effort in pursuit of a breakthrough for the new colony (Welsh) arising in the lower valley of the Chubut river, making it easier to move the products that the colony marketed with Buenos Aires and Wales.
On July 28, 1865, comes ship "Mimosa" with 153 Welsh immigrants to the shores of Golfo Nuevo (now Puerto Madryn) and they established a few kilometers further south on the left bank of the river Chubut, Rawson founded. Since then, several contingents are filed in the lower valley of the Chubut River (VIRCH), devoted to agriculture.
In what is now the city of Trelew there were three farms of the Welsh Colony belonging to Lodwig Williams, Peter Jones and Jasiah Williams. In 1867, they resolved the great pitfall of drawing irrigation channels.
In addition, they faced serious difficulties in the marketing of products, especially wheat, which was of excellent quality, so much so that they were awarded several times. Thus was born the idea of building the railroad that would link the valley with Bahía Nueva (now Puerto Madryn). The initiative of the Welsh was received favorably by the Government and the October 20, 1884, the Act 1539, authored the railway works.
In the second half of 1886 began the laying of the tracks from both ends, Trelew and Puerto Madryn. About 250 unmarried workers under the direction of engineer Jones Williams, taking advantage of the existence of freshwater and the benefits of relief (compared to the Lagoon Chiquichano) that protected the site from bad weather and the periodic flooding.
On May 25, 1889 was officially inaugurated on Central Railway Chubut, marking the beginning of a new population, then around the station there was born a place where they established the first trading houses and activities such as a bank, post office, transport, hotels, workshops, working as a service area of agricultural activity that developed in the valley.
Trelew depended on the municipality of Gaiman, like Rawson. Only in 1903 was created by decree signed by President Julio A. Roca and the Interior Minister J.V. Gonzalez, the city of Trelew. On April 18, 1904 met the first Municipal Council consisting of five members Patagonian pioneers, and was elected the first mayor of Trelew engineer Jones Williams.
The original "Rails End" area was named by settlers as Trelew, which in Welsh means saying "people of Lew", Tre = town, and Lew = short for Lewis, due to Lewis Jones, lead manager of the concession to build rail. It was officialized by Decree of the Executive Branch on October 20, 1915.