Sorry - no picture visible.

I thought I posted a picture but guess not. Will try again. I noticed another yard while I was babysitting my grandson, this is 20 miles from my house. Another persons lawn covered with these seedlings. Above the yard were a number of big maple trees, so I think they have to be maple seedlings, even though the initial leaves don't look like maple leaves at all.

Looks like maple seedlings. Many seedlings start off with "baby leaves" or cotyledons that don't look like the plant's true leaves. Kind of like baby teeth in babies that eventually get replaced by our real, permanent teeth. :)

FataMorgana

Here is a link that might be useful: wikipedia cotyledon

Yes, agree - they look like maple seedlings.

Thanks for your input. We've lived here over 30 years and I have not seen these before, and especially not in the numbers like these. My lawn is covered with them, and they are in every other little space, every garden, cracks in the sidewalk, etc. Must have been an especially good winter or spring (condition) for these to sprout like this. I love maple trees, but not THESE many!