I didn't see a while lot to add to mdern history's main page that eeither hasn't been, or doesn't need to be added to the main history level first. The particular centuries are a different matter.
In the 16th century, I added or reviewed links to human geography, occupations, education, and social types I also added a link to Ethiopia, which pushes Egypt into Asia and Vietnam into Southeast Asia.
For the 17th century, I added links to the same first four subjects. There would have been a link to Turkey, but that was already in place. But it pushes Ethiopia into Africa and Nigeria into Western Africa, which weren't in place yet.
For the 18th century, I added links to those same first four subjects. There would have been a link to Iran, which pushed Turkey into Asia and Egypt into the Middle East, if those weren't already in place. This is also the leading edge of progress backward into the past. Most of the page I liked to were already in place and developed to where I wanted them, there wasn't much real progress.
For the 19th century, I expanded the connection to human geography, and added one to occupations. The others were already sufficiently developed. This already had a link to Thailand, so there wasn't need to add one.
The mid 19th century got a link to religion, to Tokyo, and to the United States. (The Mexican War, for anyone keeping track). Adding cities at the same time I add nations will complicate things a bit, but hopefully not too much.
The late-mid 19th century got a link to behavioral culture and government. From this point, I'm adding links to cities that ought to be there if I had been adding cities from the start, so Tokyo and Seoul. Adding China pushes the United States into Western Civilization and American Indian peoples: the US Civil war and reconstruction go in this period.
The Late 19th century has links to Conceptual and behavioral culture and to government: Most of the others I wanted were already in place. Adding Mexico City pushed Tokyo and Seoul into Asia, and adding India to the list of nations pushed China into Asia. This was the period when China came close to being carved up by European powers.
In the 20th century, most of what I wanted to add had already been added, but France would have been the next nation.
The Early 20th century included new links to material culture, economics, and an update of links to it from social structure and change and social change pages. Since many nations had already been added, This would have included Indonesia, pushing India to Asiatic peoples and China into Oriental peoples. Adding New York City would push Mexico City into Western Civilization and American Indian peoples.
The early-mid 20th century included new links to all three major areas of culture, economics, and the updates from social structure and change, and social change pages. Adding Bombay would push New York City into Western Civilization. Adding Brazil would push Indonesia into Asiatic peoples and India into South Asian peoples.
The mid 20th century got the links to and from other ares I mentioned with the previous period. Adding Delhi would push Bombay into Asiatic peoples, which would push Seoul into Oriental peoples. Adding Pakistan would push Brazil into Western Civilization, which would push the USs into Anglic peoples, and it would also put Brazil with American Indian peoples, and the United States into the North American Indians.
The late-mid 20th century got the same batch of other areas linked. Adding Sao Paulo to the city list, pushed Delhi into Asia, and Bombay into South Asia. Adding Bangladesh would push Pakistan into Asiatic peoples, which would push Indonesia into Southeast Asia. This has the effect of calling to attention that I have mostly ignored the recent history of Pakistan, so there's a gap I want to make up when I next look at Pakistan.
The late 20th century was already linked to most of the areas I wanted to add. Adding Shanghai would have the effect of pushing Sao Paulo into Western civilization. Adding Russia would push Bangladesh into Asiatic peoples and Pakistan into South Asian peoples.
The early 21st century already has all the links I wanted to add. Adding Los Angeles would push Shanghai into Asiatic peoples, which would push Delhi into south Asia, and Bombay into India, where it rightly belongs, which creates a solid link between a nation and a city for this particular period. Adding Nigeria pushed Russia into Western civilization and Brazil into Latin peoples (Also bringing Mexico City with it).
With this pass through history done, I'm in a better position than before to turn to study of what I call Sociology.