San Juan de Nicaragua, formerly known as San Juan del Norte or Greytown, is a town and municipality in the Río San Juan department of Nicaragua.

https://en.wikipedia.org/wiki/San_Juan_de_Nicaragua

One source reported that Platt's Hall opened in 1860. Jack Tillmany reports that the first newspaper accounts of events there that he found were in July 1862. The building was on the NE corner of Montgomery and Bush.

It's listed in an 1882 "Guidebook and Street Manual." It was still operating as late as 1885. The Mills Building was later on the site.

http://sanfranciscotheatres.blogspot.com/2019/01/platts-hall.html