Here is a great website (in Spanish) on early baseball put together by César González Gómez, featuring original research by him and others. The focus is on Latin America, although there is some material on the Knickerbockers and other topics in early U.S. baseball history. There’s lots of excellent stuff here on early Mexican baseball, and also on Esteban Bellán, the first Latin American (and Cuban) major leaguer.
According to César, Bellán was actually a naturalized U.S. citizen, and applied for a U.S. passport in 1874. (Maybe this was already known by historians, but I had not heard of it.) After reading César’s article, I went and dug up Bellán’s application, made on January 2, 1874 under the name “Stephen B. Bellan,” in case anybody wants to see the actual document:
And here is the supporting document, Bellán’s certificate of naturalization, sworn to just three days earlier (on January 2, 1874), which is included with the passport application:
As César points out, the passport application provides Bellán’s exact birthdate, October 1, 1849, which I don’t think we had before (at least it’s not in any of the reference sources I know about, which list his birthdate simply as 1850). Here it’s listed as October 1, 1849.
On a whim, I typed “Stephen Bellan” into Google. Lo and behold, the top mention is from the New York Times archive: in the Times of September 19, 1867, Bellán was listed among the passengers arriving in New York from Havana on board the steamship Morro Castle.
UPDATE 5/23/2008 As noted in the comments, John Thorn was actually the one to first find this aspect of Bellán’s life, reporting it on the 19CBB list last November.