His father was a lawyer named Edwin A. Prosser and his mother was Esther A. Elsworth.

Halley received a public school education in Lansing and South Lyon, Michigan.

In 1889, Halley passed the Michigan Board of Pharmacy's examination.

[2] In Flushing, Prosser worked as a clerk in the drug business for around four years.

[3] In the book The Men of '05, editor Harry M. Nimmo poked fun at Prosser's weight and nosiness among other perceived character flaws.