Can someone direct me to maker of custom-sized mattresses in or near Washington state? I am trying to replace irregular shaped mattresses for a built in bed built in the 1930s. Thank you!!
Hi D Black, and welcome to The Mattress Underground 
Glad to have you here.
That sounds like a very cool project! Unfortunately, due to the high volume and turnover in businesses over the last few years, we no longer offer geographical listings of mattress manufacturers or showrooms. You may want to take a look at these prior forum posts on custom mattresses in WA state in post reply #2 here and also in post reply #5 here though the information may be somewhat out of date.
You don’t say where in Washington you are located, or what specific materials you are looking at for your custom mattress, but Trusted member of the site MFC is Located in Delta BC, south east of Vancouver; they are excellent at providing customizable mattresses and sleep systems for boats and RVs, and they also have a dedicated forumhere. Perhaps other consumers who live in the area can also chime in.
I wish you success on your project,
Basilio