Question: What interstate does Interstate 15 cross after Butte, Montana?

Context paragraphs:
Silver Bow, Butte: Silver Bow is a neighborhood in Butte, Montana, United States.  It lies near the interchange of Interstate 15 and Interstate 90, near Rocker.  Silver Bow is at Exit 119 off I-15, near the Port of Montana.  It is well known locally as the location of the Silver Bow Twin Drive-In.  Silver Bow has no school.  The school is located approximately 2 miles west in Ramsay.

Elk Park Pass: Elk Park Pass, elevation 6352 ft , is a mountain pass on the Continental Divide in southwestern Montana, about 4 mi northeast of Butte.  It is traversed by Interstate 15 and is one of three crossings of the Divide by the Interstate (all in Montana), the others being Monida Pass (on the border with Idaho) and Deer Lodge Pass southwest of Butte.  Elk Park Pass lies on the border between Silver Bow and Jefferson counties and is remarkable for its highly asymmetrical nature.  The approach from the north is through namesake Elk Park, a high, mostly treeless plain (like South Park in Colorado or the Sierra Valley in California), and the grade is almost imperceptible.  The elevation at the northeast end of the park, about 10 mi from the pass, is about 6200 ft , only 152 ft lower than the pass itself.  However, at the south end, the highway drops 750 ft from the pass into Butte over a distance of only about 4 mi .

Interstate 15 Business (Great Falls, Montana): Interstate 15 Business is a Business loop of Interstate 15 in Great Falls, Montana, USA.  The route links I-15, which bypasses downtown Great Falls to the west, to the center of Great Falls.  As its Business Loop designation implies, I-15 Business terminates at I-15 (concurrent with U.S. Route 89 and Montana Highway 200 through western Great Falls) at each end.  The southernmost 0.83 mi of the route from the interchange with I-15 to Fox Farm Road is designated, but not signed, as Interstate 315.  It is the second shortest interstate in the country; only the unsigned Interstate 878 is shorter.

Interstate 15 in Montana: In the U.S. state of Montana, Interstate 15 continues onward from Idaho for nearly 400 mi through the cities of Butte, Helena and Great Falls, intersecting with Interstate 90, Interstate 115 and Interstate 315.  Interstate 15 reaches its northern terminus at the international border with Alberta, Canada.

List of suffixed Interstate Highways: Currently the Interstate Highway System includes seven suffixed routes that are signed: the Interstate 35 split into Interstate 35E and Interstate 35W at Dallas-Fort Worth, Texas; a similar split into Interstate 35E and Interstate 35W at Minneapolis-St.  Paul, Minnesota; as well as Interstate 69C, Interstate 69E and Interstate 69W in South Texas; in addition, Interstate 480N in Ohio exists and is designated as such on mile markers but is otherwise unsigned.  However, there were once many more, as the three-digit Interstates were not designated until after all major routes were assigned numbers, including some short connections and spurs.  (A few of the shortest, including I-190 and I-195, were assigned three-digit numbers almost immediately.)  Most were not equal splits like on I-35, but had the main route continue through, and often the suffixed route never returned to its parent.  In 1980, AASHTO abolished the majority of suffixes due to confusion, renumbering them as three-digit Interstates, but several that return to their parents were kept.  For example, Interstate 15E has since become Interstate 215, but both I-35E/I-35W and I-69 splits still exist.

Deer Lodge Pass: Deer Lodge Pass, elevation 5879 ft , is a mountain pass on the Continental Divide in southwestern Montana, about 11 miles southwest of Butte.  It is traversed by Interstate 15 and is one of three crossings of the Divide by I-15 (all in Montana), the others being Monida Pass (on the border with Idaho) and Elk Park Pass north of Butte.  Unlike most other passes in western Montana, Deer Lodge Pass is in the midst of treeless, rolling hills (reminiscent of Interstate 80 in Wyoming), and the grades on the highway are relatively gentle.

Interstate 115: Interstate 115 (I-115) is a very short auxiliary Interstate Highway which connects Interstate 15/90 to Butte in the U.S. state of Montana.  The highway is 1.19 mi long and is overlapped by Business Interstate 15/90 for its entire length.  The route travels from an incomplete interchange with I-15/90 through generally rural areas in western Butte.  It interchanges with Excelsior Avenue before terminating.  The entire route was improved to interstate standards during the 1960s, and was improved in 2005.

Interstate 15: Interstate 15 (I-15) is a major Interstate Highway in the western United States.  I-15 begins near the Mexico–US border in San Diego County and stretches north to Alberta, Canada, passing through the states of California, Nevada, Arizona, Utah, Idaho, and Montana.  The interstate serves the cities of San Diego, Las Vegas, St. George, Salt Lake City, Pocatello, Idaho Falls, and Butte.  It also passes close to the urban areas of Orange County, California, Los Angeles County, California, Provo, Utah, Ogden, Utah, and Helena, Montana.  The stretches of Interstate 15 in Idaho, Utah, and Arizona have been designated as the "Veterans Memorial Highway".

Interstate 15 in Idaho: Interstate 15 (I-15) is a part of the Interstate Highway System that runs from San Diego, California, to Sweetgrass, Montana.  In Idaho, the Interstate Highway runs exactly 196 mi from the Utah state line near Woodruff north to the Montana state line at Monida Pass.  I-15 is the primary north–south highway of Eastern Idaho.  The Interstate Highway connects Pocatello and Idaho Falls, the fourth and fifth largest cities in Idaho, and the smaller county seats of Malad City, Blackfoot, and Dubois.  I-15 connects all of those cities with Salt Lake City to the south and Butte to the north.  The Interstate has business loops through McCammon, Inkom, Pocatello, Blackfoot, and Idaho Falls.

Alberta Highway 4: Alberta Provincial Highway No. 4, commonly referred to as Highway 4, is a 103 km highway in southern Alberta, Canada that connects Highway 3 in Lethbridge to Interstate 15 in Montana, and is the southernmost portion of Alberta's Export Highway.  It begins at Alberta's busiest border crossing in Coutts, winding north through gentle rolling hills and farmlands in the south of the province.  It bypasses Milk River, Warner and Stirling before reaching Lethbridge where it becomes 43 Street and ends at Crowsnest Trail on the east side of the city.  In 1995, it was designated as part of the CANAMEX Corridor that links Canada to Mexico and the United States, including the major cities of Salt Lake City, Las Vegas, Los Angeles, and San Diego which lie on Interstate 15.  In 1999, the highway was renamed the First Special Service Force Memorial Highway in honour of elite soldiers who travelled to Helena, Montana for training in preparation for World War II.  Between Lethbridge and Highway 61 near Stirling, Highway 4 is signed as part of the Red Coat Trail, a historic route stretching from southern Alberta into Manitoba that is advertised as that which was travelled by the North-West Mounted Police.

Supporting paragraphs: Silver Bow, Butte Interstate 15 in Montana
Answer: Interstate 115