After graduating from Deerfield Academy, he earned a bachelor's degree in 1955 in business and engineering management from the Massachusetts Institute of Technology. He earned a master's degree in business, also from MIT, in 1958.
He was the owner of Eacker Associates, a construction projects consulting firm, and some of his work included projects at Newton-Wellesley Hospital and Tufts University.
He worked for the Rouse Co. as a senior project manager and later was promoted to vice president, a position he held from 1979 to 1988.
Mr. Eacker, who lived in Clarksville for a year before moving to Ellicott City in 1981, was a staunch advocate not only of his family and friends, but also for his community and the environment. In 1990, he helped establish the Howard County Conservancy, later serving as trustee and president.
He was also director and treasurer of Preservation Howard County Inc. and had been director, executive vice president and president of the Howard County Citizens Association.
From 1993 to 1998, he was executive director of the Environmental Fund for Maryland, and from 1998 to 1999, was acting chair for the state Economic Growth, Resource Protection and Planning Commission.
As a master gardener, Mr. Eacker participated in the Bay Wise Landscape Management Committee and enjoyed working in his home garden. He also was an active volunteer with the Lazarus Foundation, a nonprofit computer-refurbishing organization.
He enjoyed tinkering in his workshop but most enjoyed his environmental work, family members said.
Plans for a memorial service are incomplete.
Surviving are his wife of 57 years, the former Georgia Hafner; a son, Douglas Eacker of Manassas, Va.; a daughter, Suzanne Eacker Curran of Great Falls, Va.; a sister, Eugenia Olson of Peoria, Ill.; and five grandchildren.