It’s important to know that the elevated train system in the city of Chicago is officially known as the “L,” not “el.” — because baseball fans heading there in October to watch the first Cubs-White Sox World Series since 1906 might need to know the correct way to spell the public transportation between the two ballparks.

An L series is creeping into the thoughts of Chicagoans as the Cubs, as expected, and the White Sox, incredibly unexpected, are in first place in their respective divisions. The guess here is that the search is on for the slim chance that there is a 110-plus-year-old baseball fan still alive who was on hand in ’06 as the Sox downed the Cubs 4-2 to win the title that year.

It’s shaping up to be a heck of a summer in the Windy City, as managers Joe Maddon and Robin Ventura try to steer their teams into — and through — the playoffs to make the town the center of baseball attention this fall.

Even MLB Commissioner Rob Manfred, speaking with reporters last week at U.S. Cellular Field, acknowledged what it could mean for the city — and the league.

“We are proud of all 30 of our markets,” Manfred said. “They’re all important to us. There is no doubt that our largest markets, when they are successful, they’re good for our overall business. I think the idea of having two really good teams in a major market like Chicago is particularly exciting. It creates the prospect of postseason play that could be compelling, and it’s a great thing, a great thing for Chicago.”

The Cubs were considered World Series favorites soon after Kansas City won last year’s title. They have talented veterans such as first baseman Anthony Rizzo and center fielder Dexter Fowler and pitchers Jon Lester and Jake Arrieta. Their young players — third baseman Kris Bryant, shortstop Addison Russell and infielder Javier Baez — are tantalizingly gifted. The Cubs entered the weekend leading the majors in runs scored and staff ERA.

But the rise of the White Sox is even more impressive. Chicago made several roster moves after the 2014 season but finished fourth. They made more moves after last season, and they are clicking. Signing Austin Jackson allowed Adam Eaton to move to right field, which has bolstered the defense. Mat Latos (5-0 with a 2.62 ERA after Friday’s 10-4 victory over the Twins) has been one of the free-agent steals of the year. Brett Lawrie already has walked 17 times this season after drawing just 28 all of last year.

For this Southside-Northside battle to happen, the White Sox might be more challenged to sustain their current pace. But the clubhouse vibe appears to be strong, even as the team distanced itself from the controversy surrounding first baseman Adam LaRoche, who retired during spring training rather than leave his son at home more often.

Both teams in first place through five weeks allows two things to happen. One, the interleague games between the clubs will be watched like never before. Two, fans can dream about what could happen in October.

They can dream about an L series.

Central intelligence

Indians: Cleveland can make the case that it has the best shortstop in baseball. As of Thursday, shortstop Francisco Lindor’s 5.7 WAR was the best of any player at his position over the past calendar year.

The Twins will see for themselves next weekend when they visit Cleveland for a three-game series.

Tigers: In one offseason, Detroit’s bullpen has gone from sore spot to bright spot. Closer Francisco Rodriguez has had some struggles, but setup men Alex Wilson, Justin Wilson and Mark Lowe have been excellent. Detroit’s relievers entered the weekend with a 2.67 ERA that was fourth best in baseball. Justin Wilson has a 1.50 ERA.

Royals: Third baseman Mike Moustakas is battling a bruised/jammed left thumb. He was held out of the lineup Monday and limited to pinch hitting Tuesday, then placed on the 15-day disabled list Saturday morning.

White Sox: Tears were flowing in the streets around Target Field when the Twins learned John Danks had been designated for assignment. Danks was 7-15 with a 5.76 ERA in his career with the Twins, but Chicago now is looking for a new fifth starter. Righthander Erik Johnson is getting first crack at the spot, but the White Sox have other options.

The 3-2 pitch

Three observations ...

• Detroit’s Nick Castellanos is the latest example of how some prospects take longer than others to realize their potential. He’s only 24 years old but has more than 1,100 at-bats.

• Houston must already regret sending Vince Velasquez, an impressive 23-year-old righthander, as part of a package to Philly for reliever Ken Giles.

• Any future Star Wars tributes at MLB parks should never include Jar Jar Binks, the worst character in the history of the series.

... and two predictions

• Look for at least two Nationals starters to fade down the stretch because of their workload during the first half of the season.

• The Rangers will be in first place in the AL West by the end of the month.