は...です

I think it's は. 1. 私の出身は(アメリカの)Washington D.C.です. 2. Q: Elleさんのご出身はどちらですか. A: (私は)Washington D.C.です.

@ikuko ありがとう！Your explanation is very helpful.

I think in this context, the particle " は" would be suitable. However, if the native Japanese say this expression, we would say 〝　私は　日本の出身です　or 私は　日本出身です。". and If I ask someone where you are from, we would say "　あなたは　どちらの　ごしゅっしんですか。　あなたは　どちらから　いらっしゃたんですか”. If you want to say where you are from, you shouldn't add ご　to this sentence. ご　is a kind of honorifcs. In Japanese, when we say about ourselves, we wouldn't say " 私は、ご出身は　　です。”　but we would say "私は、　　　出身です。” You are competent in Japanese. I'm surprised to see you can use Kanji and hiragana perfectly. Amazing!

は　　　。