Later 1700s - "Aguk Chongdo" (我國摠圖)

The map below is the "Aguk Chongdo" (我國摠圖) from the "Yeojido" atlas, which is believed to have been made sometime in the later part of the 18th century. The atlas is stored in Seoul National University's Gyujanggak Museum of Korean Studies.

One of the interesting things about the map is that it shows Ulleungdo (鬱陵島) with a neighboring island labeled as "Udo" (于島), instead of "Usando," which was much more common on old Korean maps.

The following is a closeup of Ulleungdo (鬱陵島) from the above map. Notice that it has a neighboring island labeled as "Udo" (于島).

Below is another Korean map from possibly the 1800s that also shows Ulleungdo's neighboring island labeled as "Udo" (于島). The map was called "Jeop-yeok Jeondo" (鰈域全圖) and is stored in the U.S. Library of Congress.

The following is a closeup of Ulleungdo (鬱陵島) from the above map. Notice that its neighboring island was labeled as "Udo" (于島).

Another old Korean map that showed Ulleungdo's (鬱陵島) neighboring island labeled as "Udo" (于島) was the "Joseon Jeondo" (朝鮮全圖), from the "Haedongdo" (海東島) atlas, which is stored in the Samseong Art Center. The atlas is believed to have been compiled at the end of the 18th century.

Below is a closeup of the Ulleungdo section of the above map. Notice that Ulleundo's neighboring island was labeled as "Udo" (于島).

The following Korean map of Ulleungdo (鬱陵島) was an inspector's map that is believed to have been made sometime in the early 1800s or before. The map shows Ulleungdo with neighboring islands labeled as "Big Udo" (大于島) and "Small Udo" (小于島). The Big Udo was Ulleungdo's neighboring island of Jukdo (竹島), which is about two kilometers off Ulleungdo's east shore, and the Small Udo was Ulleungdo's neighboring island of Gwaneumdo (觀音島), which is only about 100 meters off Ulleungdo's east shore. The map is stored in Korea's Samcheok Museum.

The following is a closeup of the "Big Udo" (大于島) and the "Small Udo" (小于島) on the above map.

Below is a Korean inspector's map of Ulleungdo that is believed to have been made sometime in the early 1800s or before. The map shows Ulleungdo with two islands labeled as "Big Gando" (大干島) and "Small Gando" (小干島). The Chinese character "Gan" (干) was a common misspelling of "U" (于) and vice versa. Again the map shows that "Big Gando" was Ulleungdo's neighboring island of Jukdo (竹島), which is about two kilometers off Ulleungdo's east shore, and "Small Gando" as Ulleungdo's neighboring island of "Gwaneumdo" (觀音島), which is only about 100 meters off Ulleungdo's east shore. The map is stored in the National Library of Korea.

The following is a what the Takeshima Research Center (竹島問題硏究所) has said about some of the above maps HERE in Question 5:

質問５

アメリカの議会図書館に、鬱陵島の隣島に于島と書かれた地図があるようだ（http://dokdo-or-takeshima.blogspot.com/2008/06/1800s-map-of-korea-jeop-yeok-jeondo.html?showComment=1212594900000）。これは三陟博物館と韓国中央図書館の鬱陵島圖形の大于島小于島と関係があるのではないか。　

回答

貴重な情報をご提供くださりありがとうございました。ご教示いただいたブログ上で地図を確認しました。三陟市立博物館と韓国国立中央図書館所蔵の「鬱陵島圖形」の「大于島」「小于島」と関係があるというのは、（１）大于島、小于島が鬱陵島沿岸の小嶼（たぶん竹嶼と観音島）であることは間違いない、他方（２）朝鮮全図で鬱陵島の東側に于山島または于山という島を描く地図についてその于山島（于山）が独島だという主張とそれも竹嶼だという主張が対立していた、（３）今回紹介された米国議会図書館所蔵の地図は朝鮮全図でありながら鬱陵島の東側に描かれた一島を「于島」と表記しているので１の鬱陵島図形と２の多数の朝鮮全図をつなぐ役割を果たす、つまり２の類型の于山島も１で明らかなとおり竹嶼だということになる、だから重要だ、というご指摘だろうと思います。すでにビーバーズさんの発見にかかる「海長竹田／所謂于山島」と記した小嶼を描く鬱陵島図や、周囲に10朝鮮里の目盛が入っていて于山までの距離感がわかる青丘図など多くの朝鮮地図によって鬱陵島の東側に描かれた于山島（于山）が竹嶼であることが明らかになっていますが、今回ブログに掲載された地図により、18世紀以降の朝鮮地図にある于山が独島ではなく竹嶼であることが、また別の角度から裏付けられたということでしょう。（事務局：総務課）