Inter-league baseball play began in 2001 and the National League Houston Astros faced the American League Texas Rangers in the first-ever “Lone Star Series” (also called “Lone Star State Series”).  New York City’s baseball rivalry has been called a “subway series” since the 1920s when the New York City American League and National League teams met in the World Series. Many other series (Chicago White Sox vs. Chicago Cubs; Kansas City Royals vs. St. Louis Cardinals) have also had regional nicknames applied.
 
The name “Lone Star Series” appeared in several newspaper articles in 1998, when the possibility of such a series was seriously discussed. The winner of the series receives the Silver Boot trophy, and the series itself is sometimes also called the “Silver Boot Series.”
   
     
Wikipedia: Lone Star Series
The Lone Star Series is an annual Major League Baseball contest featuring Texas’ two major league franchises, the Texas Rangers of the American League and the Houston Astros of the National League. It is an outgrowth of the “natural rivalry” established by MLB as part of interleague play.
 
The winner of the 6-game series is awarded the Silver Boot. A 30-inch tall display of a size-15 cowboy boot cast in silver, complete with a custom, hand-made spur. If the series is split (3-to-3), the winner is the club which scored the most runs over the course of the series. Under the current rules, the designated hitter is used at the Rangers’ home games but not at the Astros’ home games.
 
Austin (TX) American-Statesman
A Lone Star State Series? Well, maybe
Author: MICHAEL A. LUTZ ASSOCIATED PRESS  
Date: May 19, 1998 Publication: Austin American-Statesman (TX) Page Number: C5 ${ Word Count: 680
HOUSTON -- Is it too early to start thinking about an all-Texas World Series? Yes, but the way the Texas Rangers and Houston Astros whizzed through the first month and a half of the season has them pointed in the right direction. If they're still charging at the All-Star break, the topic surely will come up again.

The Rangers and Astros have traveled parallel paths this young season. Both had club-record victory totals for April, both started May with divisional leads and ...

MySA.com
Lone Star Series a real possibility (September 29, 1998)
Jerry Briggs Express-News Staff Writer   San Antonio Express-News
Sports Page 1C (992 Words)
In a state that worships games played by large men in pads and helmets on October afternoons, another sport has moved into the Lone Star spotlight. It’s baseball. And if you don’t believe it, take a look at the major- league playoff schedule. For the first time in history, Texans can brag about both of their teams being in postseason competition.
 
“Hey, it’s about time, right?” asked Houston Astros first-base coach Jose Cruz.
 
10 June 2001, Paris (TX) News, pg. 1B, col. 2:
Texas also drew even in the first-ever “Lone Star Series” with its cross-state rival, pleasing the 49,603 fans who made the largest regular-season crowd in the seven-year history of The Ballpark.