ARCHEOLOGICAL MANIFESTATIONS IN THE 
TOOLE COUNTY SECTION OF THE TIBER RES- 
ERVOIR BASIN, MONTANA? 
By Caru F. Minter 
INTRODUCTION 
The Tiber Dam, sometimes known as the Lower Marias Unit, had 
its inception some 50 years ago when William T. Cowan, State Senator 
from Hill County, Mont., stumped for the construction of a dam across 
the Marias River, the waters of the subsequent reservoir to be used 
for irrigation purposes. His was a far-sighted vision, one which 
was not fully appreciated until many years after his death. 
On September 30, 1952, President Harry S. Truman, before a crowd 
of 10,000 people, set off a blast marking the ground-breaking for 
the project. The dam, located 68 miles upstream from the confluence 
of the Marias and the Missouri Rivers, is a rolled earth-filled structure 
4,300 feet long, with a maximum height of 205 feet and a maximum 
width at the base of 1,282 feet. The lake to be formed will have a 
surface area of 22,180 acres with a maximum length of 25 miles and 
a maximum width of 4 miles. 
A concrete spillway chute, 1,334 feet long and varying in width from 
108 to 200 feet and with walls ranging from 10 to 51 feet high, is 
designed to pass flood waters of greater magnitude than have thus 
far been recorded in the area. Over the spillway is an operating 
bridge on which are located the hoists, motors, and controls for oper- 
ating 3 radial gates, each 32 feet wide and 20 feet high, controlling 
the spillway discharge. There is also a highway bridge over the 
spillway to accommodate traffic across the dam from the connecting 
roadsystem. (See map 5.) 
The Lower Marias Unit is a multipurpose development with irriga- 
tion as its major function. It will bring under cultivation approxi- 
mately 991 farms in sections of Hill, Liberty, and Chouteau Counties. 
Included in the list of crops to be irrigated will be small grains, peas, 
flax, potatoes, sugar beets, and alfalfa; also, there will be an in- 
crease in the acreage of pasture lands. Other functions of the dam 
and reservoir will include flood control, the supplying of 3,600 addi- 
1 Submitted February 1955. 
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