In a newer development you’d be lucky to have 6 inches of fair to poor topsoil over fill when the builders were done with it. The old houses were probably built on good farmland to begin with.

My 1837 house had feet of beautiful topsoil. My current 1938 home also had several feet of good soil, truckloads of it carted away when we had a septic, patio and garage built, and 6 inches of stony crappy yellow “topsoil” brought back. I can barely get a shovel in it to plant anything.

I’m not sure how much just mowing will do for the soil unless you are leaving clippings and chopping leaves, and maybe topdressing occasionally. Areas that are gardened with compost added and wooded areas where leaves are allowed to breakdown would build good soil over time.

I topdressed a lawn I had with compost and aerated regularly, and always mulched clippings and as many leaves as I could without smothering the grass and the soil seemed pretty happy, but it was good deep soil to begin with.

Sure, gardening and growing and mowing might build a deeper soil over time, but that's probably minor. Most likely it's the point that Saypoint mentions: older houses were mostly built on or near agricultural land, since that's what people did for a living. It will depend a lot on location, but the chernozem type (black earth) / grasslands soil can be over a metre deep - it's accumulated organic material from many, many decades (centuries). I read recently that there's proportionally more organic material growing/deposited/accumulating 'underground' - i.e. the root systems - in grasslands than aboveground. Now it's all levelled, cleared, removed, then replaced.

I bet mowing grass does not do much for the soil, unless you are mowing deep rooted weeds. It is deep roots that build the soil, whether they are from weeds or trees.

There was definitely (in general) less mechanical grading and removal of topsoil in the old days. It was only the invention of backhoes and bulldozers that made it possible to cheaply and quickly move huge amounts of soil.

Thanks for the comments! It just dawned on me when I was watching that show last night.

gg, thanks for the clarity definitely meant structure or quality.

glib, what is actually happening with the deep rooted weeds as you mow them? Are they digging deeper? I am keeping a certain % of weeds to help aerate the soil and deliver the sugars to the soil

tox, that makes sense. I bet they are not going as deep with the foundations as they do today and re spreading as much subsoil as well.

My lot was farmland. To my displeasure roughly 1/3 had the top soil removed and subsoil added during development of the land and then was farmed again when the lot sat for 8 years. I only knew that as dug a 20" deep hole, hit subsoil then towards the bottom was was looked like a grassland material. They also too much of my subsoil and spread it even in areas where the top soil wasn't stripped. I should have just had the subsoil taken off site but didn't stay ahead.

In another 1/3 of the lot I hit roughly 18" of sandy loam, then hit 12" of silt. Water tends to makes its way back there too so things grow quick lush in that area. I wish I had that for the entire lot!

I always bring that up when helping out my dad at his garden and public garden he tends... I never seem to hit "sub soil". Their neighborhood is very very old. On the other had my newer home is built on old farmland and has horrible subsoil below the sod. I agree with Tox... it had to have been different building practices. Both homes are in clay territory... both homes had basements.

As an example of building practices vs soil - I've been to many cities where the difference between older parts of town and newer parts where subdivisions dominate is striking. Older houses / older streets: every house can be a different level, with different numbers of steps up/down to the door or basement, and the streets have (dramatic or modest) up and down inclines. Every house is different, sometimes they just built into the hills on the spot. (The lots will also vary in size/shape sometimes). Newer subdivisions (if you can see them being prepped for building): the rolling up and down contour of the land is just flattened in advance, bulldozed almost level. Streets are absolutely flat.

I'm not making some big anti-modern point, just the pretty obvious one that after they do this, not surprising the soil might look nothing like 'topsoil' anymore. They weren't trying to make a place for gardens and soil (lawns at best).

Of course, on lots with older houses you might have variance too, like the case above (noticeably siltier in some areas, more clay in another). You might also have lots where the soil's been improved by human habitation - old outhouses or even much older cesspits, middens, old compost piles, woodsheds, firepits, etc - at least in places, the difference in soil might be quite noticeable.