Disabling utf-8 in all terminals?

This question pertains to my Ubuntu 18 system, as follows ... % uname -a Linux myhost.name.net 4.15.0-45-generic #48-Ubuntu SMP Tue Jan 29 16:28:13 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux I don't know how long the following has been going on in the midst of my regular system upgrades, but I have now noticed that all my terminal windows are writing UTF-8 characters. I want all terminal windows to use us.ascii (or possibly iso-8859-1). I can't find anywhere where this is set. Furthermore, all keyboard input seems to be coming in as UTF-8, and I also want it to be us.ascii or iso-8859-1. By default, the LANG variable is set to en_US.UTF-8 in all shells that run in my terminal windows, but I am not knowingly setting it that way within any config files. This occurs under xterm, rxvt, and urxvt, and none of these programs are configured to utilize UTF-8, that I know of. I'm running XFCE4, if that makes any difference. I can't find any settings for this in the XFCE4 settings, either. Can anyone suggest a way to reset my system so that all terminal windows always display us.ascii or iso-8859-1, and all keyboard input is also us.ascii or iso-8859-1? Thank you very much.