In the early 1950s, McCleary, Washington was one of several locations in an:
"American peacetime operation aimed at determining the ability of the airdropped propaganda leaflet to spread information" (quote source).The name of the overall project was Project Revere and the name of the specific experiment McCleary was in was Operation Eight Towns.
Project Revere was an Air Force and University of Washington operation. Test 1 used eight communities in western Washington that were small, reasonably close to Seattle, and locations that would be taking in refugees if larger cities were attacked.
McCleary was Town H, population 1,175. Necessary local authorities were contacted before the leaflet drop, they agreed to keep information out of the media until the experiment was done. Aerial photos and maps were created prior and then on a Wednesday around noon, leaflets were dropped by plane over the town, unannounced. In McCleary the greatest number of leaflets were dropped - about 35,000.
Two light planes were used for McCleary because of the large quantity of leaflets. One plane at a time, with pilot and a leaflet dropping crew of two. I haven't yet found out the exact date of this McCleary drop, it would have been some time between 1951 - 1953.
The leaflets stated:
"One raid by an enemy bomber could paralyze... radios - telephones - newspapers. In such a disaster leaflets like this could be dropped from airplanes to give official instructions. You are an important part of this scientific test to find out how effective leaflets are for spreading vital information to everyone."Readers were asked to be modern day Paul Reveres and help spread the word. A survey was also included and postage was paid so participants could mail the leaflets in as instructed.
The next Saturday (media still not talking about the drops) face to face interviews were done.
Some findings of the overall project were that children were univerally the fastest and most thorough at picking up the leaflets. 4-8 leaflets per person were found to be the sweet spot of message diffusion. Also in some locations the color yellow did not work for the leaflets, aphids were attracted to the color and covered the leaflets. Photos of aphids on leaflets could be used as counter propaganda by an enemy.
Altogether, Project Revere dropped approximately 750,000 leaflets involving 51 message versions in 44 flight missions over 35 unwarned communities. In the process of this experience a list of 50 measurable factors which might influence the accurate distribution of leaflets on the ground was compiled. These 50 factors concerned only the plane-to-plane speed, packaging, wind and weather, visibility, timing (day and hour), terrain, population density, drop patterns, etc. The experience of the Project developed some information on many of these patterns. (source The Flow of Information: An Experiment in Mass Communication, by Defleur, Melvin L.;Larsen, Otto N.)
DeFleur, M. L., Larsen, O. N. (1958). The Flow of Information. New York: Harper
Dodd, Stuart Carter. (1959). Formulas for Spreading Opinions. The Public Opinion Quarterly, 22(4), 537-554.
Hertzler, Robert L. (1953, November 29). Measuring Firepower of "Paper Bullets". The Seattle Times
Pearson, J. Bruce. (1957). Message diffusion under uncontrolled conditions. Boulder: University of Colorado Press
Thanks to SGM Herbert A. Friedman (Ret.) for insights