John Fillmore Hayford was an eminent United States geodesist.

His work involved the study of isostasy

Isostasy

Isostasy is a term used in geology to refer to the state of gravitational equilibrium between the earth's lithosphere and asthenosphere such that the tectonic plates "float" at an elevation which depends on their thickness and density. This concept is invoked to explain how different topographic...

 and the construction of a reference ellipsoid

Reference ellipsoid

In geodesy, a reference ellipsoid is a mathematically-defined surface that approximates the geoid, the truer figure of the Earth, or other planetary body....

 for approximating the figure of the Earth

Figure of the Earth

The expression figure of the Earth has various meanings in geodesy according to the way it is used and the precision with which the Earth's size and shape is to be defined. The actual topographic surface is most apparent with its variety of land forms and water areas. This is, in fact, the surface...

.

The crater Hayford

Hayford (crater)

Hayford is a lunar crater on the Moon's far side. It is a relatively isolated feature with the nearest named crater being Krasovskiy, some 300 km due south. Hayford has a well-defined edge that is not significantly eroded. The inner walls slope directly down to the floor, with little slumping or...

 on the far side of the Moon

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

is named after him.

A biography of Hayford may be found in the Biographical Memoirs of the National Academy of Sciences, volume 16(5), 1935.