William M. Sachs, 90, a partner in a Washington real estate and insurance firm who was active in church and other organizations, died Monday at the Westwood Retirement Home in Bethesda after a heart attack.

Mr. Sachs was born in Baltimore and moved to Washington with his family in 1900. The family had a bakery in Southwest Washington and his first job was driving a horse and wagon to make deliveries for it.

He later opened a haberdashery near the Marine Barracks in Southeast Washington. About 1916, he opened a furniture store at Eighth and D streets NW. In 1934, after prohibition had been repealed, he opened a liquor store at 15th and G streets NW. Shortly thereafter, he became a builder and real estate developer.

In 1942, Mr. Sachs and one of his sons, David, acquired the Geo. S. King Co. and operated it as a partnership dealing in real estate and insurance. Mr. Sachs remained a partner in the company until his death.

Mr. Sachs was a member of the Washington Board of Realtors. He also was an organizer and the first president of the D.C. Retail Liquor Dealers Association. He was a founder and past president of the Amity Club in Washington.

He also was a past president of the B'nai Israel Congregation when it was in Washington. (It has since moved to Rockville). For about 70 years he was a member of the Ohev Sholom Congregation in Washington. Among the organizations to which he made charitable contributions were the Greater Southeast Community Hospital and The American University.

His wife, the former Rebecca Krumpsaw, to whom he was married for 69 years, died last Dec. 31.

Survivors include two sons, David, of Washington, and Sidney S., of Silver Spring, six grandchildren and eight great-grandchildren.