The sound came churning out of Chicago like a screaming locomotive. A scratching rhythm guitar that resonated like a drum and a raspy voice singing “Bo Diddley got a diamond ring …” That was a half-century ago and the man behind the music is still singing about that ring and headed up the road toward Rockland.

Legendary rocker and guitar master Bo Diddley will be the headliner at this weekend’s North Atlantic Blues Festival on the city’s waterfront.

Bo Diddley has been moving fans with his unique sound of chunking guitar and driving vocals since the early 1950s. He was nicknamed “The Originator” after his twin-sided single “Bo Diddley” and “I’m a Man” went to the top of the rhythm and blues charts, months before Bill Haley and the Comets and Elvis Presley had their chart-busting debuts.

The man born Ellas Bates in McComb, Miss., and known to the world as Bo Diddley will close out the festival with a Sunday afternoon performance that will begin at 4:30 p.m.

Diddley is one of those unique performers who not only has a signature song, but a signature look and band. Backing up the 73-year-old legend will be the Debby Hastings Band, featuring two female musicians. He also will bring along his magic box of special effects, such as reverb, tremolo and distortion, that make Bo Diddley’s patented square, pointed, oblong and rocket-tailed custom-built Gretsch electric guitars scream and howl.

As is the case every year, blues impresarios Paul Benjamin and Jamie Isaacson have put together a stellar lineup featuring legendary blues players and promising newcomers.

With Bo Diddley topping the bill on Sunday and Austin, Texas, guitar great Jimmie Vaughn matching him on Saturday, this ninth version of the North Atlantic Blues Festival promises to be one of the best. An estimated 14,000 are expected to attend the two-day festival.

“It’s a good solid lineup,” said festival founder Benjamin. “We’ve really put together a great mix of people.”

Benjamin has a right to be proud of his creation. The festival has taken the best festival award in Blues Audience Magazine’s readers poll and this year Benjamin and Isaacson received the industry’s “Keeping the Blues Alive: Promoters of the Year” award for 2002 by the Blues Foundation in Memphis. The Keeping the Blues Alive awards recognize nonmusicians for their role in supporting blues music.

“It puts us in a group of the best promoters in the world as voted by our peers,” said Benjamin. “Other winners were blues festivals in San Francisco, New Orleans, Chicago and now Rockland, Maine. We must be doing something right.”

Along with the North Atlantic Blues Festival, downtown Rockland restaurants and clubs hire bands and open their doors each weekend night for the popular Club Crawl. The city shuts down Main Street (Route 1) and converts it into a pedestrian mall, with live bands on every corner and music blaring out of every eating spot. The Club Crawl takes place Friday and Saturday nights.

Saturday’s show opens at 11 a.m. with Mary Dukes, a traditional Chicago-style gospel-blues singer. She will be followed by South Side Slim, a fixture on the West Coast blues circuit for the past 30 years. Taking the stage after Slim will be the Bubba Mac Blues Band, featuring 1998’s Apollo Theater Rookie of the Year Award winner Teri Showers on vocals.

Little Charlie and the Nightcaps will follow with their blend of blues, rockabilly and bebop led by guitarist Little Charlie Baty and harmonicist Rick Estrin. Next up will be Lucky Peterson and his gritty, soul-infused blues and then by James Cotton, the legendary guitar and harmonica player who has been on the road since the 1940s. Closing Saturday’s show will be Jimmie Vaughan, a founding member of the Fabulous Thunderbirds whose roadhouse blues style has thrilled concertgoers since the 1970s.

Sunday’s show opens at 11 a.m with Maine native and vocalist-saxophonist Pat Pepin, with Big Chief as her backing band. Pepin will be followed by Sean Costello, a 22-year-old Philadelphian who cut his teeth on the music of Jimi Hendrix but got hooked on the blues early on and has evolved into one of the top up and coming guitarists in the country. Following Costello will be John Primer, a Chicago blues guitarist who is best known for his work with Magic Slim.

Blues harmonica legend Carey Bell will be up next, followed by Deborah Coleman, one of the leading lights of the next generation of blues artists. Coleman is a singer-songwriter who also plays a mean lead guitar. Closing the show will be the great Diddley.

Ticket prices are $25 each day. Tickets for children 6-12 years old are $5, children 5 and under are free. For information, call 593-1189 or go to www.northatlanticbluesfestival.com.