The individual Census Takers who would visit your home or farm were given a list of codes for each possible place you may have been born.

Keep in mind that the United States of 1890 was very much a country of immigrants. Many of those immigrants were coming (or had recently come) from Europe. The trip would take around 7 days¹ , even by the fastest steamships in 1890, so the census list actually has two separate codes for those people born at sea. One for those born at sea in international waters (code is "Go") and one for those born at sea under the U.S. flag (code is "Dp"). (see below)