What dropdown are you talking about?

If it's the address bar; Type about:preferences#privacy<enter> in the address bar.

The button next to History, select Use Custom Settings.

Turn on Remember My Browsing And Download History At the bottom of the page, turn on Clear History When Firefox Closes. At the far right, press the Settings button. Turn on ONLY Cache and Form And Search History leaving the others off.

Yes it is in the address bar.

The problem is not clearing the history from my Mac firefox, but clearing the history that shows up from my iPhone firefox in the address bar even after clearing the history from the firefox on my iPhone. Seems some are "stuck" in my mac even if I deleted the firefox app from my iPhone

Did you follow my instructions above? That will clear the form fill data.

Yes ... went back and checked and quit Firefox and started it up and the iPhone sites are still listed. When I click in Clear Recent History in the menu and include also clear Browsing and Download History and then quit and restart, they are still there

I called for more help.

I finally fixed it

I looked under pref for my Mac firefox and clicking on the Firefox Account opened Manage account and then looked at devices and applications and saw there were two listed for my iPhone. One had a sync date older than the other and deleted the old one and the problem went away Also saw there were some older ones for my ipad, even thought it was not a problem and deleted the old ones. I've re-sync both and only one of each in the device list.

That was very good work. Well done. Please flag your last post as Solved Problem so others will know.