The Irish Mill Inn is a roadside haunt that makes you wonder what's happening inside. And not necessarily in a good way.

But the erstwhile establishment, which is celebrating its 75th year, is a classic case of looks being deceiving.

Hard to miss because of the windmill atop the entrance, the building and an adjoining home stand apart in a timeless stretch of unincorporated area across the street from Diamond Lake near Mundelein.

Its rough exterior belies what you find inside - a mix of old-timers and newcomers who favor the pub-like atmosphere and Irish touches.

Located on busy Route 60/83, the Irish Mill can be an impulse stop, though over the years it has remained essentially a neighborhood tap.

Some regulars have been dropping by for 30 years. Most everyone in the area either knows of the place or has been inside, particularly on St. Patrick's Day, when hundreds pass through and snarl traffic more than usual.

There's no hard proof to pinpoint the origin of the place originally called the Dutch Mill, near a former resort area on what used to be called Route 59A.

One chapter of its history will be celebrated this weekend when former owner Linda Patterson is the special guest at an annual benefit for her late husband, Dom. Proceeds benefit children's burn camps. Call (847) 566-7044 or visit www.irishmillinn.com.

Scraps of information from amateur sleuths and old stories that have evolved into lore are the basis of the historic acknowledgment. A Google search reveals an old newspaper listing of the county board issuing a liquor license for the "Diamond Lake Dutch Mill" in 1933.

O'Neill's Tavern on Route 59A in Mundelein is listed in a 1940 phone book. But Fremont Township records show the house and tavern were built in 1943. In 1947, there is a phone listing for Hackett's Dutch Mill tavern in Diamond Lake. One newspaper accounts says the tavern started as a convenience store with gas pumps.

What is correct? Who knows?

Some say it operated as a speak-easy before Prohibition ended in 1933 - the first year taverns could legally obtain a liquor license.

"I wouldn't doubt it was probably open during Prohibition," says Patrick McGrath, a chatty college professor who bought the place a year and a half ago. "To our knowledge they stood in line to get licensed the next day."

Character without glitz is what snared McGrath, who has been making improvements to attract newcomers to the sizable pool of established patrons. The faithful have been coming for years for the fish fry and live music.

He speaks of an early owner who had a talking crow. Then there was the 80-year-old woman who insisted on coming in for a beer before the bar opened one day early in his tenure.

"I always stop here for a beer on my birthday," she told McGrath. She hasn't been in since.

"I expect to see her when she's 81," he says.

Sociable and adventurous, McGrath was looking for a different lunch option when he stepped in out of curiosity and left entranced with the possibilities.

After buying the bar on a handshake deal, McGrath, who teaches mental health counseling at National-Louis University, spent a substantial amount replacing the floor, paneling, bathrooms and kitchen.

His son, Justin, who has a culinary degree from Kendall College was installed as chef and general manager. His menu has traditional bar fare as well as homemade shepherd's pie and Guinness beef stew. Additional dishes are planned.

McGrath expanded the deck out back facing heavy woods and a large pond that feeds Diamond Lake and is working on a horseshoe pit and space for bocci. Dart leagues are big and the bar sponsors a softball team. Activities like Wednesday night trivia have found a following.

"New people kind of find us," he says.

That would be folks like Anna and Joe Villafane of Buffalo Grove, who spotted the Irish Mill Inn on a spring ride.

"We drove by and said, 'That place looks neat,'" said Anna. "We felt very welcome. You walk into the place and you feel like you're at home already."

No doubt the shabby exterior and perceived sense of the mischief or worse within has deterred many would-be patrons over the years.

There is no official entrance or paved parking lot. Just pull off the road and claim a spot - the front door is not much more than a car length away from the main road.

Outside, the tiny building is a bit the worse for wear, although McGrath is working on that, too. The awnings are beyond cleaning, even with bleach. The shutters droop. Wood is rotting. Although it is on a major road, it certainly looks off the beaten path.

What type of welcome would a stranger get?

Even some regulars who have frequented the old tavern for decades, say they initially were afraid to find out.

"It looks a little rough and it used to be worse," explains Mark Janaes, who has been stopping for the Irish music and camaraderie for about 25 years. He passed for three years before deciding to give it a try.

Indeed, the Irish Mill's motto, available on T-shirts, is: "The Place You'll Meet Friends You Didn't Know You Had."

Whitey O'Day, a singer who has entertained in the cramped confines periodically over 30 years, said the tavern was "a bit more primitive" when he started coming in 1973.

"A lot of people were afraid to go in there," he said. But old-timers and the work crowd settled in during the day and a younger set filtered in at night but never was there trouble, he added.

Formerly known as the Dutch Mill tavern, the name was changed when John and Angie Burns bought it in 1973 the when it was still considered in the sticks. The Burns owned it until the early 1990s.

"People thought we were mad," said Angie, an accomplished darts player.

"It was a great gathering place for young and old. Everybody knew everybody who walked in the door."

They introduced darts, real ones, to the Irish Mill, which later became the dart headquarters for the Windy City and Northern Illinois dart leagues. The boards and plaques that go with past victories occupy a prominent nook near the bar.

If the green and white exterior, shamrocks carved into the windmill blades, the Irish flag and a second flag denoting an Irish regiment in the Civil War don't give you a hint, of the interior is filled with curiosities large and small that scream Irish.

The sign above the bar, "Ceaomile Failte," translates to "a hundred thousand welcomes."

Family coats of arms are affixed to lattice above the bar. A sign in one corner reads Irish wolfhound Way, a tribute to McGrath's dogs and the mascots of Tullamore Dew, the house whiskey.

McGrath is moving ahead with more improvements, which should be good news for the customers.

"We don't really own it," he says. "We're caretakers. They define the culture."