The first post office in Nauvoo was in Sidney Rigdon's kitchen. Later, it was moved to the Elias Smith Print Shop. Often they were in Dry Goods Stores. This "mail box sorter" was in Nauvoo when the Saints were here. It's now back. Just a bit of trivia that I didn't know--people could either pay their postage up front or have the person who was receiving it, pay for it. Therefore, a lot of mail was left unclaimed. The prophet Joseph Smith used to get a lot of hate mail COD, so he had to take out ads in newspapers which essential said, "If you're sending me hate me, pay for it yourself, I'm not going to claim it". Postage across the USA would cost one fourth of a day's wages and they didn't use envelopes.