Looking for a website to create large format maps.

I don’t know if this would help Essential backpacking maps: types, online platforms, software, and printing tips

If you have Adobe Acrobat X or XI you can print directly to a PDF file from the mapping software. Most architectural firms use Adobe Acrobat.

It looks like you can print any size you want from Caltopo. I don't see why that wouldn't work, though I haven't tried it yet.

You might have to stitch files together if you want something that's not a rectangle, and that could be more difficult.

If you are making huge files with Caltopo you might consider donating to the site to help cover some bandwidth and server costs. It's really cool that the service is available for free, but it would be nice to help out the guy that runs it if you can.

I exported as a jpg, and shipped it to the 48" printer.
Done.

If you like maps, and don't mind learning some new things – QGIS is free open source GIS software. Nearly all the base maps that caltopo has can be displayed and you can customize to your hearts content. But, it would take awhile to learn. I'd only go this route if you are into maps and might use it for other things in the future.

I still use caltopo because it is simple and does what I need.

-Peter

Thanks, all. I should have clarified that printing isn't the issue – I can export a PDF of some of the layers on Caltopo (but not Google Maps, which is the best for showing highways.) Part of the struggle is to get a long skinny image with enough resolution to be usable. I'll keep experimenting with some of these sites.