The population of Latvia today is estimated at 1.9m, slightly below the 1.95m census population of 1935, and falling since a high of around 2.7m in 1989 ([WP][1], citing the Latvian statistical bureau). I *believe* these figures reflect a consistent geography and the boundaries have not substantially changed since 1920, but I haven't been able to precisely confirm that.

Many Baltic and Eastern European states show a similar pattern, but none quite match your 1950 cut-off. Estonia and Lithuania have had a similar but less pronounced population decline since peaks around 1990, and the last time they had their current populations was probably circa 1965-70. Hungary's population now is comparable to its population in the mid-1950s. In the Balkans, Bosnia & Herzegovina and Serbia have populations now comparable to their populations in the late 1960s. All of these are still falling gradually.


  [1]: https://en.wikipedia.org/wiki/Demographics_of_Latvia