Keeping an old house clean? I feel like I'm losing my mind.

I'm living in an old (just shy of 100 years old) house for the first time, and I don't know if it's just that the house hasn't had a proper scrub down in years, a product of the house itself (drafty and whatnot), or just the fact that I'm not living alone for the first time in a long time, but everything is constantly dusty or dirty. The baseboards, tile ledges, window sills, pony walls, chair rails, etc. all seem to have a new layer of dust or grime every time I turn around. We don't have central air, and the heat hasn't been on. We haven't had any home construction, either.

Am I missing something? Is there a trick to keeping things clean in old homes?