paragraph_text: The city grew out towards the west of the boundaries of the peninsula formed by the River Aare. The Zytglogge tower marked the western boundary of the city from 1191 until 1256, when the Käfigturm took over this role until 1345. It was, in turn, succeeded by the Christoffelturm (formerly located close to the site of the modern-day railway station) until 1622. During the time of the Thirty Years' War, two new fortifications – the so-called big and small Schanze (entrenchment) – were built to protect the whole area of the peninsula.

paragraph_text: Coordinates: 47 ° 00 ′ 01 ''N 109 ° 45 ′ 04'' W ﻿ / ﻿ 47.00028 ° N 109.75111 ° W ﻿ / 47.00028; - 109.75111 ﻿ (State of Montana) Area code 406 is the telephone area code covering the entire state of Montana. It has been Montana's area code since area codes were created in 1947.

paragraph_text: Eagleby is a suburb of Logan City in Queensland, Australia located on the southern bank of the Logan River at the juncture with the Albert which forms the southern and eastern boundary. The Pacific Motorway marks the western boundary. Eagleby is northeast of Beenleigh, and was originally a suburb of Beenleigh.

paragraph_text: Galloway is an unincorporated community west of the city of Columbus in southern Prairie Township, Franklin County, Ohio, United States. The 43119 ZIP Code, however (which carries a Galloway mailing address) covers a significant portion of rural and suburban western Franklin County, as well as parts of western Columbus, and locals might use the name Galloway to refer to any location in the area roughly bounded by I-70, Galloway Rd, Alkire Rd, and Big Darby Creek; such a location is seldom in the community of Galloway proper. The Galloway Post Office is located within the city of Columbus about two miles north of the actual community of Galloway, which lies at the intersection of Galloway Road and Sullivant Avenue.

paragraph_text: Montana is one of the nine Mountain States, located in the north of the region known as the Western United States. It borders North Dakota and South Dakota to the east. Wyoming is to the south, Idaho is to the west and southwest, and three Canadian provinces, British Columbia, Alberta, and Saskatchewan, are to the north.

paragraph_text: Area code 207 is the North American telephone area code for the state of Maine, excluding Estcourt Station which uses Quebec province's overlay of 418 and 581.

paragraph_text: Blanco is a rural unincorporated community located on State Highway 63 in Pittsburg County, Oklahoma, United States. The ZIP code is 74528. The Census Bureau defined a census-designated place (CDP) for Blanco in 2015; the 2010 population within the 2015 CDP boundary is 96 and contains 52 housing units.

paragraph_text: Blackwater Township is one of fourteen townships in Cooper County, Missouri, USA. As of the 2000 census, its population was 406.

paragraph_text: Eastport is an unincorporated community in Boundary County, Idaho, United States. Eastport is located at the Canada–US border along U.S. Route 95, across from Kingsgate, British Columbia and north of Moyie Springs. Eastport has a post office with ZIP code 83826.

paragraph_text: Seneca is an unincorporated community in Union County, New Mexico, United States. Seneca is located on New Mexico State Road 406 north-northeast of Clayton.

paragraph_text: Bayville is an unincorporated community located within Berkeley Township in Ocean County, New Jersey, United States. The area is served as United States Postal Service ZIP Code 08721. As of the 2010 United States Census, the population for ZIP Code Tabulation Area (ZCTA) 08721 was 20,512. Central Regional High School is the local high school for the area.

paragraph_text: The Lincoln Mountains is a mountain range in southeastern Alaska, United States, located on the Alaskan side of the Portland Canal between the Salmon River and the Soule River, near the community of Hyder. It has an area of 235 km and is a subrange of the Boundary Ranges which in turn form part of the Coast Mountains.

paragraph_text: The County of Tatchera is one of the 37 counties of Victoria which are part of the cadastral divisions of Australia, used for land titles. It is located to the south of the Murray River, and to the south west of Swan Hill, with its western boundary at 143°E, and part of the southern boundary at 36°S.

paragraph_text: Elston is an unincorporated community in Cole County, Missouri, United States. It is located near the western boundaries of Jefferson City.

paragraph_text: Wayland is an unincorporated community in western Paris Township, Portage County, Ohio, United States. It is located at latitude 41.161 and longitude -81.071, with an elevation of 948 feet. Although it is unincorporated, it has a post office, with the ZIP code of 44285. The community is part of the Akron Metropolitan Statistical Area.

paragraph_text: North American area code 509 is the telephone area code for the eastern two-thirds of Washington. The western boundary of 509 roughly follows the Cascades. The 509 area includes Spokane, the Tri-Cities (Richland, Pasco, and Kennewick), Ellensburg, Yakima, Walla Walla, and Wenatchee. The 509 code was created in a split from 206, originally the area code for all of Washington, in a flash-cut on January 1, 1957.

paragraph_text: Illinois is in the midwestern United States. Surrounding states are Wisconsin to the north, Iowa and Missouri to the west, Kentucky to the south, and Indiana to the east. Illinois also borders Michigan, but only via a northeastern water boundary in Lake Michigan. Nearly the entire western boundary is the Mississippi River, except for a few areas where the river has changed course. Illinois' southeastern and southern boundary is along the Wabash River and the Ohio River. Whereas, its northern boundary and much of its eastern boundary are straight survey (longitudinal and latitudinal) lines. Illinois has a maximum north - south distance of 390 miles (630 km) and 210 miles (340 km) east - west. Its total area is 57,918 square miles (150,010 km).

paragraph_text: There are over 42,000 ZIP Codes in the United States. ZIP Codes are used not only for tracking of mail but also in gathering geographical statistics in the United States. The U.S. Census Bureau calculates approximate boundaries of ZIP Codes areas, which it calls ZIP Code Tabulation Areas (ZCTAs). Statistical census data is then provided for these approximate areas. The geographic data provided for these areas includes the latitude and longitude of the center - point of the ZCTAs. There are approximately 32,000 ZCTAs. The reason that there is not one ZCTA for every ZIP Code is that PO Boxes are excluded, since only populated areas are included in the Census data. The Census Bureau provides many statistical data sets for ZIP Codes, but does not keep up - to - date datasets of all ZCTAs. Complete datasets providing a similar approximate geographic extent are commercially available.

paragraph_text: The Ochoco Mountains are a mountain range in central Oregon in the United States, located at the western end of the Blue Mountains. They were formed when Permian, Triassic, and Jurassic rocks were slowly uplifted by volcanic eruptions to form the Clarno Formation. Today, the highest point in the range is Lookout Mountain. The dominant vegetation on the west side of the range is old-growth ponderosa pine; on the east side, western juniper is common. The western area of the mountains is administered by the Ochoco National Forest, while the southeastern section is part of the Malheur National Forest. The Ochoco Mountains are used for hiking, camping, bird watching, rockhounding, and hunting, as well as cross-country skiing in the winter.

paragraph_text: Sheridan is a census-designated place in Placer County, California, United States. It is located at the western edge of the county, along State Route 65. Sheridan is northwest of Lincoln. Its ZIP code is 95681 and area code 530. The elevation is . The population was 1,238 at the 2010 census.

Question: What U.S. state forms the western boundary of the state where area code 406 is located?
Answer: Idaho