Ken,
I live on Horace Greeley Road three houses down from Horace Greeley's birthplace
which has been fairly sympathetically preserved as a private home.  (The owners
are planning to spend their retirement years as lily farmers.)  HG's concrete
house piqued my interest and I found the following:
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From the Portland Cement Association's web page at
http://www.portcement.org/news/3.htm#8:
Probably the oldest recorded concrete house was built in Milton, Wisconsin, in
1844 by William Goodrich. A tradesman and inn-keeper, Goodrich wanted a home
safe from Indian attacks and arson. Used first as a home, then as a stagecoach
inn, the building has massive load-bearing walls and a distinctive six-sided,
three-story tower.
Today, the Milton House, its hexagonal tower still intact, is a local museum. At
150-years-old, it's still in excellent condition.
Greeley's Barn Becomes a House
Horace Greeley, famous editor, farmer, and adviser of young men, is the next
concrete builder of record. In 1852 (or 1856 as sources vary), he built a
three-story concrete barn on his estate at Chappaqua, New York. The concrete
consisted of a heavy mortar in which stones and oyster shells were embedded.
After Greeley's death, the barn was remodeled into a house named "Rehoboth"
where his daughter lived until her death in 1937. Since then, new owners
extensively remodeled the house. It is still used as a private residence.
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Also, the Canadian Portland Cement Association at
http://www.cpca.ca/house_pubs.html is advertising a poster showing historic
concrete houses.

Lisa