https://www.usgs.gov/the-national-map-data-delivery/gis-data...
They have full US coverage and many infill sets at higher resolutions.
They have 1 metre DEMs ( ~ one elevation per three foot x three foot square )
https://www.sciencebase.gov/catalog/items?q=&filter=tags=Dig...
and more if you get to know their community and products (they are a firehose of likely more data than many can afford to reliably store).