Black and white photograph of a girl, Mary Burkhead, sitting on a chair on grass next to a house.

Black and white photograph of a boy, David Burkhead, sitting on a chair on grass next to a house. His eyes are closed.

Black and white photograph of a boy and a girl, David and Mary Burkhead, sitting on chairs on grass next to a house.

Black and white photograph of a boy and a girl, David and Mary Burkhead, sitting on chairs on grass next to a house.

Black and white photograph of a man standing behind a partially constructed sewer trench.

Black and white photograph of four men and a tractor working on an archaeological excavation site.

Black and white photograph of four men and a tractor next to a creek. A field is visible behind a pile of dirt.

Black and white photograph of a man sitting next to a hole in the ground writing on a piece of paper. A mastodon rib is visible in the hole surrounded by measuring sticks.

Black and white photograph of a mastodon rib bone in dirt next to a ruler.

Black and white photograph of a field in front of a dirt area next to a forest.

Black and white photograph of a field in front of a dirt area next to a forest.

Black and white photograph of a Tzolk'in calendar chart on paper.

Black and white photograph of the Maya Sun Calendar Cycles, published by the Eugene Dietzen Co. of Chicago and New York.

Black and white photograph of a ladder with two adjustable legs over a measuring grid square on grass. Part of a camera ladder rig system developed by Merrill for taking overhead photographs of archaeological excavations. Flowers and trees are…

Black and white photograph of a ladder with two adjustable legs over a measuring grid square on sand. Part of a camera ladder rig system developed by Merrill for taking overhead photographs of archaeological excavations. A cottage is visible behind…

Black and white photograph of a ladder with two adjustable legs over a measuring grid square on sand. Part of a camera ladder rig system developed by Merrill for taking overhead photographs of archaeological excavations. A cottage is visible behind…

Black and white photograph of a ladder in front of a tree next to a cottage. Part of a camera ladder rig system developed by Merrill for taking overhead photographs of archaeological excavations.

Black and white photograph of two metric measuring grid squares next to a measuring stick on sand. Part of a camera ladder rig system developed by Merrill for taking overhead photographs of archaeological excavations.

Black and white photograph of two metric measuring grid squares next to a measuring stick on a rug. Part of a camera ladder rig system developed by Merrill for taking overhead photographs of archaeological excavations.

Black and white photograph of a beach next to forest from above.

Black and white photograph of a tree-lined pathway next to a building with a large seaside building visible in the distance next to the path.

Black and white photograph of a seaside city with a mountain in the background.

Black and white photograph of a seaside city with a road leading to the city between the sea and a park.

Black and white photograph of a raised cement structure on a shoreline. A courtyard is visible in the distance with a monument in the center. Stone stairs can be seen behind the monument. A stone towers built into the cement wall on the left side of…