I've established Elves in the EMP campaign as a mostly nomadic people. If we take a lesson from Farm, Forge, and Steam to heart, we learn that "population dense agriculture trump[s] population diffuse nomadism (hunter-gatherer/herding). Always." So we create a little contradiction here, how have Elves remained a nomadic people through antiquity to the early modern period while sharing the continent with humans?
Let's pull in another source, Noel Perrin's Giving Up the Gun: Japan's Reversion to the Sword, 1543-1879. Perrin describes how Japan 'gave up the gun' after mastering the technology due to the impacts guns had on the existing social structure as it pertained to the Samurai and ruling classes. While not all critics agree with Perrin, it does create interesting fodder for my Elves.
Instead of having Elves as a nomadic civilization since antiquity, we can instead have them as nomads only recently. They rejected the growing tide of cities, proto-industrialization, proto-nationalism, and the consumption of natural resources by returning to semi-nomadic roots.
As a side note: demi-human races are not going to be long lived like in standard D&D tropes. The whole human/demi-human experience throughout history would be radically different if people were living hundreds or thousands of years. While I could make concessions to fit extended lifetimes into the game, I would rather go the other route and give all races a similar life span.
This idea also leaves plenty of room for PCs and their characters to agree, disagree, or disregard their race's position. There are plenty of sub contexts that players can riff off of if desired. So let's take a crack at that lore again:
The Elves as a people developed as hunter gatherers, ranging out into the forested fringes of Europe from Ireland through northern Germany to Russia.
Elves developed their civilization and society in relative proximity to early, pre-Roman humans, with a mixed history of competition, cooperation, and warfare that characterizes the typical clash of civilizations. The Romans viewed the Elves as 'barbarians' just as much as native humans in the ever expanding frontiers of the Empire. The Elves varied in their response to the Romans, with integration, extinction, and migration all being common.
Over time, Elven people began to more closely resemble their human neighbors, even to go so far as to cross-breed in enough numbers that Half-Elves were recognized as a race unto itself. However, a backlash was in the making.
The Dark Ages was just as trying for Elves as it was for humans, with the upheaval of Muslim conquests, the Migration Period, and the changes in society since the decline of the Roman Empire. With the Black Plague and recurring famines of the 14th century, Elven society took a dramatic step.
Blaming the seemingly irreversible tide of civilization, Elves sought to retreat from the strife and suffering that seemed common in a period of ever more frequent peasant revolts, the Hundred Years' War, and recurring epidemics and famine. This retreat was literal, with the majority of Elves picking up and moving farther away from cities and feudal lords and back into the wilderness of their ancestors.
Today, Elves have struggled to re-integrate into a semi-nomadic, hunter-gatherer society. A heavy reliance on Druidism and nature magic has helped them adjust, but it remains to be seen how this experiment will ultimately impact the race as a whole.
Elves who take up the life of an adventurer will find many opportunities to exploit their keen senses, talent for martial arts and magic use, as well as their connection with nature.