Here are some useful databases for studying the urban history of Seoul (and other parts of Korea).*
The Seoul Museum of History has old maps of Seoul (and other places) that can be downloaded. As well, the Museum has published several books about specific neighbourhoods you can read online (for example, Itaewon or Dongdaemun Market). And of course this collection of 1946 US military maps is also useful.
Maps can also be found at this Seoul-oriented website. At top right you can see a button with an airplane reading ‘정사영상’ [ortho-rectified aerial image] which features aerial photos from various years between 1978 and 2020. (These are great because they stitch numerous aerial photos together into one map, but one drawback is that the maps from earlier years leave out downtown Seoul; photos of downtown can be found at another website mentioned below, however.) Meanwhile, the button at this site above the airplane one, ‘지도전시관’ [Map exhibition] brings up a menu with maps from various eras, including one that reads 서울시 전재표시도[1950년대] and is titled “War-Destroyed Area of Seoul.” It’s the most complete such map I’ve ever seen, and even differentiates between damage caused during the North Korean invasion, occupation and expulsion (June-Sept. 1950) and that of the Chinese (Jan.-March 1951). I'll guess the version below will not be full size, so the full map I put together from screenshots can be seen and downloaded here.
This government site has aerial photos going back to 1947 (for some neighbourhoods), though it only becomes consistent and of high quality from 1972). Just search for a particular 동 and, after confirming the correct location, the 항공사진 option should appear on the menu that pops up. You can narrow the selection to a certain year or set of years, and can download full size photos if you sign up to the site.
To determine the age of buildings in Seoul, one of the easiest ways to see when a building was registered is with this 3D map, which has buildings colour coded by decade, and if you click on the building it will tell you the year it was registered (unless it is grey, which means there’s no information). Of course, the date registered and the date built don't always align, but they do often enough. It allows you to see at a glance the age of buildings in a neighbourhood. A less user-friendly property history site (but with more information) is here.
*I posted some of this material at the bottom of another post a while ago, but realized it might be useful to give it a post of its own.
