The Last Green Valley’s 23rd annual Walktober series of 106 free hikes, paddles, bike rides and other events in the 35-town National Heritage Corridor is underway, already registering more than 1,200 participants for the monthlong program.

This year’s series includes more than a dozen events in Norwich, including the “President Lincoln in Norwich” walk at 1 p.m. Monday led by Dale Plummer, city historian. The walk will start at City Hall. Themes of other Norwich walks will focus on the city’s mills, firearms factories, Benedict Arnold and wealthy residents of the past, among other topics. Also the walk will start at City Hall.

Also in the series are four walks in Preston, one at Mitchell Preserve, one to the Long Society Meetinghouse, one to a town-owned forest at the Norwich State Hospital property and one at the Rose Hill Wildlife Management Area.

The list of events can be found in the 32-page Walktober brochure, available at: www.tlgv.org or by calling (860) 774-3300.

New this year, The Last Green Valley is selling a limited edition Walktober T-shirt decorated with colorful falling leaves. The 100 percent cotton shirt can be purchased for $20, with proceeds benefitting the Walktober program. It can be purchased by visiting the on-line shop at www.tlgv.org or by calling (860) 774-3300.