Hogarth, I like that.
So my own entry ...
Hogarth-3 is an 1880 parallel, with a early-dieselpunk TL5+1 technology and a merged America and Canada. Racial equality is a given and the Indian Nations are protectorates undergoing benevolent uplift. The rest of the world is largely the same as Homeline 1880, save for technology imported from America and a more aggressive British Empire.
The very first and obvious historical change was the election of
Frederick Douglass as American President in 1860, with Abraham Lincoln as his Attorney General. This rang alarm bells immediately, as the historial records were otherwise identical to that point.
The American Civil War was a much bloodier and horrid affair in this world, with a higher death toll and plentiful atrocities. But the sheer malevolent viciousness of the Secessionists in response to "the Antichrist" made is easy after the war to purge the entire slave-holding culture, as even the majority of white Southerners were appalled. President Douglass served his two terms, followed in office by Abraham Lincoln, who died in office.
In a few years, racist thought was considered to be obnoxious and primitive. The former slave population received remedial education, revealing several previously unsuspected talents in engineering and sciences who advanced the technology of America.
In the 1870's individual provinces of Canada began requesting annexation by the US. These movements seemed to be spontaneous grassroots movements. By 1878 all of Canada save Quebec was assimilated, the US Flag had 44 stars, and British/American relations were at their lowest level since the War of 1812.
The Shelldrake Section investigators looked over everything they could, finally discovering a weak psionic energy field over North America. It appears to have a consciousness, but is incapable of controlling minds. Instead, it appears to act through memes and dreamscapes. It seemes to be responsible not only for the election of Douglass, but the ease with which the memetics of racism and bigotry were eliminated in the American culture. It may also be responsible for the technology boost.
This world is under watch, because it is unknown whether or not the Unknown Intelligence acquired any useful knowledge from parachronic visitors. Visitors are obliged to have some form of psionic shielding technology.