PETER BOODY PHOTO | Under the eye of officers from the Sherrifs Department, inmates from the Suffolk County jail began work on Wednesday preparing the site of a limestone monument to Islander Henry Howard Preston, the first paid Suffolk County sheriff.

Site work began Wednesday on the lawn in front of Shelter Island Town Police headquarters to prepare for the installation in October of a large limestone foundation stone. Salvaged from a long-gone county Sheriff’s Office that once stood in Riverhead, the stone will be placed there with a plaque honoring Shelter Islander Henry Howard Preston, the first salaried sheriff in Suffolk County from 1903 to 1906.

The  stone, and the site work, are being funded by the county Sheriff’s Office. Workers at the site Wednesday and Thursday were inmates from the county jail, which is operated by the office.

In June, the Town Board formally designated the arc of lawn in front of the police station as the Henry H. Preston Plaza at the request of a private committee formed by his descendants. Mr. Preston, a Civil War veteran who also held several local offices here, presided over the building from which the foundation stone came.

Among other achievements, he went on to establish the county’s Probation Department and to serve as a judge of the Court of Sessions.

The old sheriff’s office was torn down some years ago, his descendant Arthur Bloom told the Town Board in June. He originally proposed placing a boulder on the plaza but recently he and other descendants of Mr. Preston met Suffolk County Sheriff Vincent DeMarco at a ceremony for Sheriff’s Department workers who had died on duty. The sheriff offered to donate and transport one of the stones — saved long ago from the building demolition and preserved in storage — to Shelter Island for the Preston Plaza.