He moved to Waterbury, Connecticut, in 1881 and engaged in mercantile pursuits and the real estate business.

By resolution of the House of January 20, 1909, the seat was declared to have been vacated on January 6, 1909, for the reason that incumbent had entered upon the duties of the office of Governor of Connecticut the preceding day, however this only occurred because Lilley submitted his letter of resignation to the Governor of Connecticut instead of the Speaker of the House.

During his short tenure, he increased funding for the public school system and appropriations were budgeted for a statewide movement against tuberculosis.

He also endorsed governing monopolies and establishing a public service commission, but both issues were defeated by the legislature.

[6] Lilley was Governor of Connecticut from January 6, 1909, until his unexpected death on April 21, 1909, in Hartford.