We think that may be a Persimmons tree, which is a fruiting tree native to Maryland.
They can be spread by seeds carried/deposited/planted by wildlife, but they also 'move' by root suckers that can run. 
It's possible that a mature tree is nearby or recently was cut down.
Here is our page that includes them to learn more: 
https://extension.umd.edu/resource/less-common-fruits-home-garden/
They are attractive trees valuable to native wildlife. If you choose to keep one, you could just keep mowing the others, that should eventually control them.
For a complete kill you could carefully 'paint' the leaves with an herbicide containing the active ingredient glyphosate.  Glyphosate will kill any green plant tissue that it contacts so 
be sure to follow all label instructions carefully.


Christine