I talked about the settlement campaign a while back, and the idea has been percolating in my brain since then. What I want to do is outline, roughly, what game structures and information are necessary to run a successful settlement campaign. Alexis talks about players not choosing to settle (hah!) in favor of adventuring because the supportive mechanics don't yet exist, but I think from the DM's side of the issue, we have to know the kinds of things necessary to present that option to our players - I gave my players a square mile of land and within minutes I was scrambling to generate a whole lot of information about farming, crop yields, sufficient caloric intakes, building times, and other stuff that I hadn't prepared. They were patient as I frantically researched and deferred answering questions, but that'd be enough to dissuade most DMs from trying such a stunt again - the necessary knowledge is probably no more to learn than what a well-researched DM knows about the Medieval and Renaissance period, but because we don't know what we don't know, it seems much more daunting. In many ways it is an entirely new game because much of the rules we have do not apply or cover the situations that will arise with land management.
So, it's time to figure out what we don't know.
First, I think there are two kinds of settlement campaigns, at least starting out. The first is to expand the frontier, moving past the edge of civilization to create a new population hub. The community will still have strong ties and frequent communication with the rest of the world and serve as an extension of it. An example of this would be the European colonization of Africa - once the Europeans had the technology to move beyond the coasts, they'd gradually settle the land while keeping strong trade and communication routes to the towns behind them. The second is like the American pioneers - travelling for months before reaching their destination without a firm connection to the rest of civilization. It is about creating an entirely new, independent community.
There will be a lot in common between the two, but the major difference is the expansionary community still has access to the economic system of their community of origin. The pioneer community doesn't - they have to make, find, or do without. That crucial difference will play out in a number of subtle ways - the expansionary community will retain much of the customs and habits of their origin, whereas the pioneer community, by necessity, will need to behaviorally adapt to their new setting.
While I'm working on an economic system similar to Alexis', I don't have one yet, and my world is far less settled than his, lending more opportunities for parties to try the pioneer campaign. Therefore, I'll focus my attentions on the pioneer settlement campaign first, and come back to the expansionary campaign after I've built a stronger framework. Now, the pioneers traveled in the early 19th century, whereas the effective time period for many D&D worlds spans the 13th to 17th centuries. However, given the technology of magic and somewhat more modern social infrastructure found in most of these worlds, I don't think such a trek would be infeasible. Furthermore, I think the ability to build a kingdom from the ground up would appeal to many, many players.
There are three main phases to the pioneer campaign. The first is the physical journey to the new digs, which includes surviving the hostile wilderness and picking a good spot for the settlement. The second is the construction of that settlement, and the third is creating a larger community (via alliances, war, or just making babies and building more houses). Obviously, the community can and will develop after that, but we need to be able to handle these three stages before we can do anything else.
The physical journey is just a hexcrawl, albeit one of extraordinary length. The Oregon Trail spanned just over 2,000 miles. Remember those 20-mile hexes on my map? That's a 100-hex hexcrawl. Now, there were stops along the way, places pioneers could resupply and recuperate, but at about the 1/3rd mark, these supports fell away: Fort Laramie was, I believe, the last bastion of civilization and left the pioneers some 1,400 miles to travel, with wagons laden with all of the supplies they'd need. They'd be expected to blaze much of the trail as they traveled, making the wilderness a much more pervasive threat than most hexcrawls I've seen.
Remember Maslow's Hierarchy of Needs? The final site chosen has to provide some way of obtaining food, potable water, and a safe place to sleep. Since this is still D&D, it should also be a somewhat defensible site, and there should be a number of monster dens and ruins nearby that the party will need to clear.
Once the resources above have been harnessed and every person and animal has some kind of shelter, the settlement has been established. That's going to look very different depending upon what food and building materials are easily available, and also the weather. Roofs are only necessary when precipitation happens on a regular basis. Timber, sod, and clay bricks are commonly-used building materials. Depending upon the area's climate, different crops can be grown - rice paddies or wheat fields, root vegetables or vine vegetables, berries or orchards.
At the third stage, communities are self-sustaining and your players can look to expand their influence, either by finding other communities settled in a similar way, making the return journey to civilization to recruit more settlers, or waiting until the next generation.
This is intended to be a brief overview of the process, and I'll focus in-depth on each stage drawing out more specific mechanical needs. Just from this overview, though, we can make a list. We need a massive hexcrawl, the length and hardship of which discourages casual travel back to civilization, we need to know the climate of the settlement region as well as its ecologic, hydrologic, and geologic makeup, we need to be able to generate a number of potential settlement sites with advantages and disadvantages for each (which means we need to find a way to mechanically evaluate settlement sites), we need to determine the wild food resources available (to sustain the party until the next planting season), we need to determine the threats in the area (dungeons, lairs, large predators, etc.), and we need to determine what nonessential resources are available (ore veins, cash crops, etc.) for trade or enrichment.
See, this is the excellent thing about lists. Sure, it's a lot to cover and we have barely started examining this process, but each of these items is achievable and the whole process isn't quite as daunting anymore, is it?