The SGMA is internet based, with members all over the USA. Most of the module owning members live east of the Misissippi, so that's where the layouts have been displayed. The Dulles (Virginia) show was one of four sponsored by the World's Greatest Hobby on Tour organization this year. The location of these shows changes every year.
The trains we were running included vintage Lionel and Flyer, home builts, and modern era standard gauge marketed by multiple manufacturers, including Lionel and MTH. The shiny new "Lionel" are mostly MTH reproductions.
You missed the "Second Golden Age of Standard Gauge"! There are lots of great trains that were made after WW2.
Kirk
www.sgma.us