What datum are these tide heights measured from?

Heights are given in feet above MLLW, mean lower low water, which is the chart datum used on US nautical charts and in printed tide tables. A prediction of 2.1 feet means 2.1 feet above that reference, not above the seabed.

Why does the nearest station sometimes sit miles from the town?

NOAA maintains roughly 3,500 tide prediction stations, which is not one per beach. Each page names its station and the distance to it. Where the closest station is more than 30 miles away no tide data is shown, because timing and range change too much over that distance to be worth quoting.

NOAA CO-OPS

Tide charts and tide times

High and low tide predictions for 57 coastal stations, with observed water level compared against prediction so surge is visible.

NOAA GOES-19 GeoColor, Caribbean

AL

DE

Lewes (Breakwater Harbor) Harmonic

FL

GA

LA

MA

MD

Ocean City Inlet Harmonic

MS

NC

NJ

Atlantic City (Ocean) Harmonic

NY

PR

SC

TX

VA

VI

Charlotte Amalie, St. Thomas Island Harmonic

International

Why the station matters more than the town

NOAA maintains roughly 3,500 tide prediction stations. That sounds like a lot until you lay it against the US coastline, and it is nowhere near one per beach. So these pages are organised by station, not by city, because the station is the thing the data actually describes.

A city page links to its nearest station and states the distance. Where the closest station is more than 30 miles away, no tide data is shown at all. Tide timing and range change enough over that distance that quoting it would be confidently wrong, and a missing module is better than a misleading one.

Stations come in two kinds. Harmonic stations compute their own curve from measured constants. Subordinate stations are expressed as time and height offsets from a nearby reference station, which makes them slightly less precise. Each page says which kind it is.