Did the US military use power armor before the bombs fell? I just need to know for a mod I'm working on. Thanks!

They did have them during the war from what I've seen in Operation Anchorage.

All I found was this reference of The West Tek Research Facility:

http://fallout.wikia.com/wiki/West_Tek_Research_Facility

Researching power armor in 2069 and the war began in October 23, 2077.

K, thanks, any idea which model would be most appropriate for them to have?

Probably the T-51b

k awesome, thanks for all the help!

There's a shot of "our boys in Canada" in the fallout 1 intro:

http://www.youtube.com/watch?v=geLiEiAiQJA

How else did the U.S. military gain a foothold in China and not get thrown into the South China Sea? The T-51b was the reason troops were marching on Beijing before China and the Enclave decided it was in each other's best interests to hit the thermonuclear reset button. Read the holotape from the West-Tek facility in FO1. Could you imagine whole battalions of T-51 troopers with Fatman launchers, missile launchers, gatling lasers, and Avenger miniguns. It's like walking Rolling Thunder in my mind. Then the quaint T-45d got relegated to home-defense and riot-suppression duty before the bombs. That what Elder Lyons stumbled upon in The Citadel/Pentagon. He needed to replaced his worn out T-51s and found a stash of T-45's.

Yes, they used the T-45d (Fo3 PA) in Anchorage and then started using T-51b in China and for riot control in the US and annexd Canada.T-45 was the first truly usable model of Power Armor. T-51b was the best.

As others have said, the US Military was utilizing T-45d and T-51b suits.

The vast majority of T-51bs were either on the Chinese Mainland (Fighting the US's invasion of China in retaliation for the invasion of Alaska) or on the West Coast (Presumably awaiting shipment over to China). It's worth noting that the T-51b was the standard US Mechanized Infantry Armor at the time of the War, but it was still scarce.

The DC Area still relied on the earlier T-45d model suits, hence why that particular version is so predominant on the East Coast.