Two divisional teams separated by a few miles and state line and two fan bases who don't like each other. Those are the ingredients of good rivalry. The Cubs & Brewers rivalry will never match the Yankees & Red Sox, or even the Cubs & Cardinals, nonetheless, it is a good rivalry.
For the most the part the rivalry exists between the fans more than it does the actual organizations. The teams had played spring games, but never played each other in a the regular season until a interleague series in 1997. prior to the Brewers moving to the NL Central in 1998. For the first few years of the divisional battles there wasn’t much to get excited about on the field. The Brewers of the late 90’s and early 2000’s were atrocious. (This helped fuel the fan rivalry, but will dive in that later) The Cubs, on the other hand, fielded three 80+ win teams and one 90 win team. During that same time span the Brewers didn’t top 80 wins once. The head to head records where relatively even with each club winning 3 years and 2 ties from 1997 through 2004.
On the Field
It wasn’t until 2007 that the rivalry on the field starting getting as hot as the rivalry in the stands. The Brewers were considered legitimate contenders for the NL Central Crown for first time ever. Of course, the Cubs had plans of their own to bring home the divisional title to the North Side. The Brewers led the division by 8 games and were 14 games over 500 twice in the early goings, but when the Calendar hit September they had cooled off and the steady Cubs had climbed the ladder all the way to the top. Once again, the North Siders finished ahead Brewers in the NL Central standings, clinching on the final Friday of the season with just a few games to play. Since then the Cubs have continued to finish ahead of the Brewers in the NL Central standings except for a poor 2010 campaign. They won the crown again, by 7 games, in 2008 while the Brewers found themselves in 2nd place the for 2nd straight year.
In the Stands.
The short distance between the two stadiums (about 80 miles on I-94), the struggles of the Brewers in the early 2000’s and the loyalty of the Cubs fan base are the key ingredients that ignited this heated rivalry. With the fan turn out at horrendous levels at Miller Park, the forever faithful Cubs fans migrated north and made themselves comfortable in the newly dubbed “Wrigley Field North.” Of course this didn’t sit well with the Brewer fans, but there wasn’t much they could do about being outnumbered 2 to 1 in their home ballpark. Things started to change around 2005 when new owner Mark Attanasio made a commitment to the Milwaukee fans to take back Miller Park and field a competitive ball club. The Brewer faithful responded by packing the seats at Miller Park and a rivalry was born.