The following map of Ulleungdo comes from the "Joseon Jido (朝鮮地圖), which is a Korean atlas believed to have been made sometime between 1750 and 1768. The maps in the atlas were unique for the time because they were drawn on ruled paper for relative scale. The map below shows Usan (于山) less than two grid lines off the eastern shore of Ulleungdo. That means that it was just a few kilometers offshore. It also means that it was almost certainly Ulleungdo's neighboring island of Jukdo (竹島), which is about 2.2 kilometers off Ulleungdo's eastern shore. Korea claims that Usando (于山島) was the old Korean name for "Dokdo" (Liancourt Rocks), but the map below shows that Usando was almost certainly Ulleungdo's neighboring island of Jukdo, not Dokdo. The map is stored at Seoul National University's Kyujanggak Institute of Korean Studies.
The map also shows Ulleungdo with five other neighboring islands off the southern shore. This was most likely a mapping error since most of Ulleungdo's rock islets (石島) are off Ulleungdo's northern shore. In any case, this map, and several others, seems to conform with an 1899 Korean newspaper article, which described Ulleungdo as having six small neighboring islands, the most prominent of which was Usando/Jukdo (于山島竹島). The combining of the names "Usando/Jukdo" in the article was most likely done to show that the one island had two names, which is also what Korea's old maps tell us.