Firefox Options > General. Look for the Download option. Set it to wherever you want the download to go, or to ask you all the time.

Also, you can Go to the Mozilla Add-ons Web Page (There’s a lot of good stuff here) and search for download sorters. They can sort by web site, file extension, and many other criteria.

I'm not seeing that the browser.download.lastDir pref is reset if I only clear the browser and download history

If you do not keep changes after a restart or otherwise have problems with preferences, see:

• http://kb.mozillazine.org/Preferences_not_saved

Note that clearing "Site Preferences" clears all exceptions for cookies, images, pop-up windows, software installation, passwords, and other website specific settings.

• Tools > Options > Privacy > Firefox will: "Use custom settings for history": [X] "Clear history when Firefox closes" > Settings > Site Preferences
• https://support.mozilla.org/kb/Clear+Recent+History

See also:

• https://developer.mozilla.org/Mozilla/Preferences/Preference_reference/browser.download.lastDir.savePerSite

The value resets upon clearing my browser and download history.

I'll set it to save to "D:" and everything is fine until I either close the browser or clear my history.

Did you check for issues with the prefs.js file that stores the preferences?

I checked, and it's not saving there, either.

I tried searching around a little, and found this thread:

https://support.mozilla.org/en-US/questions/716616

hello bob_backlund, there's a general regression in firefox 27 that won't allow files to download directly into a root drive. please try to create a subfolder (like D:\Downloads) and set this as default location for downloads...

also see bug #958899.

Thanks a lot, that solved the issue.