Building handmade houses for Purple Martins became a passion of Mr. Cain during the time he worked at a transfer station in Kentucky. A transfer station is where you take used materials to be transferred to appropriate land fills. While working at the station he noticed a few things; 1) some reusable building materials were being thrown away, 2) early spring arriving Purple Martins were checking out this location for possible nesting sites as it was located in open acreage, and 3) he slowly had become fascinated with the flying martins.
When I used to visit Mr Cain, at his work space, I was received by the aerial antics of the insect-eating martins that swooped and dove in midair for their meals. I understood how one could get hooked on having a martin house in their yard.
All the above houses are part of those designed and made by Mr. Cain for his workplace. Mr Cain retired a few years ago and since then the houses have, unfortunately, been deteriorating. Purple Martins east of the Rockies need someone to take care of their housing -- approximately one million folks in eastern North America put up housing for these totally house dependent martins. West of the Rockies martins are not dependent on folks to provide housing.
Male and Female Purple Martins
Resource: YE Yard Envy
Here is an excellent site, The Purple Martin Conservation Association, that has information on such subjects as migration maps and behavior.