The Southern League did not operate during the First World War, and when it resumed for the 1919–20 season Merthyr were placed back in the top division.

Despite having finished second bottom in the season before, usually a relegation place, Merthyr became a new member of the Football League.

The 1923–24 season saw a slight improvement in league form as they finished 13th, but the major news was their appearance in the final of the Welsh Cup, though they lost 1–0 to Wrexham in a replay after a 2–2 draw.

The club dropped back into the Southern League, but lasted only four seasons, before ceasing to play in 1934.

In the late 1990s and early 2000s Newport County were local rivals but the teams have not met in the same league for many years.

A new club under the name of Merthyr Town was formed and joined the Western Football League.

[citation needed] The team reached the first round proper of the 2022–23 FA Cup, where they lost 2–0 to Buxton.

The site was once used by the Romans for their local military encampment and during the industrial revolution it became part of the Penydarren House estate.

[10] In the latter half of the nineteenth century Penydarren Park was used by the locals as an open recreational for walks, athletic competitions and team sports.

[11] An early attempt to bring rugby league to Wales, saw local team Merthyr Tydfil RLFC set up at the rival College Ground.

This in turn led to the larger Penydarren Park being host to the first touring Australian rugby league side where they faced a Wales XIII in front of a crowd of 6,000.

[12] In July 2011, the newly promoted Merthyr Town FC hosted Welsh Premier League side Llanelli in a pre-season friendly at Penydarren Park, and thereafter took up full-time residency.

[citation needed] Note: Flags indicate national team as defined under FIFA eligibility rules; some limited exceptions apply.