Where does Captain America's shield come from?

At the end of Avengers: Endgame Steve Rogers

comes back to the present

and brings the shield with him.

How did Steve manage to bring it or even possess it?

I am going in with the assumption that there is only 1 shield. It was buried in ice along with him during the events of Captain America: The First Avenger. He wields it till Captain America: Civil War and leaves it after fighting with Tony. In Avengers:Endgame, Tony gives it back to Steve. It is broken in the fight so Steve wields Mjolnir and takes it back with him at the end when he has to return the stones.

So, where did this extra shield come from?

Best Answer

As per one of the directors:

If Cap were to go back into the past and live there, he would create a branched reality. The question then becomes, how is he back in this reality to give the shield away? Interesting question, right? Maybe there’s a story there. There’s a lot of layers built into this movie and we spent three years thinking through it, so it’s fun to talk about it and hopefully fill in holes for people so they understand what we’re thinking.

This essentially confirms that Cap branched reality when he went to be with Peggy, and that he's returned to the "main" timeline (somehow) to pass on the shield to Sam.

It's therefore logical that he's brought the shield from that timeline which, since it was branched off from the original reality, likely never had the exact same sequence of events resulting in its destruction.