paragraph_text: The first full-scale working railway steam locomotive was built by Richard Trevithick in the United Kingdom and, on 21 February 1804, the world's first railway journey took place as Trevithick's unnamed steam locomotive hauled a train along the tramway from the Pen-y-darren ironworks, near Merthyr Tydfil to Abercynon in south Wales. The design incorporated a number of important innovations that included using high-pressure steam which reduced the weight of the engine and increased its efficiency. Trevithick visited the Newcastle area later in 1804 and the colliery railways in north-east England became the leading centre for experimentation and development of steam locomotives.

paragraph_text: Latvia ( or ; , ), officially the Republic of Latvia (, ), is a country in the Baltic region of Northern Europe. Since its independence, Latvia has been referred to as one of the Baltic states. It is bordered by Estonia to the north, Lithuania to the south, Russia to the east, and Belarus to the southeast, and shares a maritime border with Sweden to the west. Latvia has 1,957,200 inhabitants and a territory of . The country has a temperate seasonal climate.

paragraph_text: The GER Class 127 was a class of a solitary experimental 0-6-0 compound steam locomotive built by the Great Eastern Railway at its Stratford Works in 1888. It was rebuilt as a simple locomotive in 1895, and withdrawn in 1913.

paragraph_text: LMS diesel shunter 7050 is an experimental 0-4-0 diesel-mechanical shunting locomotive, introduced by the London Midland and Scottish Railway (LMSR) in 1934 and which remained in service with that railway for six years. It was later acquired for military use and is now preserved at the National Railway Museum.

paragraph_text: Internationally, in 1920, the RSFSR was recognized as an independent state only by Estonia, Finland, Latvia and Lithuania in the Treaty of Tartu and by the short-lived Irish Republic.

paragraph_text: Rēzekne (Latgalian "Rēzekne" or "Rēzne" , ; see other names) is a city in the Rēzekne River valley in Latgale region of eastern Latvia. It is called "The Heart of Latgale" (Latvian "Latgales sirds", Latgalian "Latgolys sirds"). Built on seven hills, Rēzekne is situated east of Riga, and west of the Latvian-Russian border, at the intersection of the Moscow – Ventspils and Warsaw – Saint Petersburg Railways. It has a population of 31,216 (2016) making it the 7th largest city in Latvia.

paragraph_text: The original Keadby railway station was the eastern-most terminus of the South Yorkshire Railway. The railway, which was extended from Thorne and opened in September 1859 was built without an Act of Parliament, as the railway company owned the canal alongside which they built the line.

paragraph_text: Skonto Stadium () is a football stadium in Riga, Latvia. The stadium has 9,500 seats and was built in 2000. It is the biggest football stadium in Latvia, and Is also home to the National Latvian team.Riga FC usually have an average attendance of 500. The stadium design incorporates Skonto Hall.

paragraph_text: There has, however, been interest among railroad operators in returning to DC use at higher voltages than previously used. At the same voltage, DC often has less loss than AC, and for this reason high-voltage direct current is already used on some bulk power transmission lines. DC avoids the electromagnetic radiation inherent with AC, and on a railway this also reduces interference with signalling and communications and mitigates hypothetical EMF risks. DC also avoids the power factor problems of AC. Of particular interest to railroading is that DC can supply constant power with a single ungrounded wire. Constant power with AC requires three-phase transmission with at least two ungrounded wires. Another important consideration is that mains-frequency 3-phase AC must be carefully planned to avoid unbalanced phase loads. Parts of the system are supplied from different phases on the assumption that the total loads of the 3 phases will even out. At the phase break points between regions supplied from different phases, long insulated supply breaks are required to avoid them being shorted by rolling stock using more than one pantograph at a time. A few railroads have tried 3-phase but its substantial complexity has made single-phase standard practice despite the interruption in power flow that occurs twice every cycle. An experimental 6 kV DC railway was built in the Soviet Union.

paragraph_text: The music and lyrics were written in 1873 by Kārlis Baumanis, a teacher, who was part of the Young Latvian nationalist movement. It has been speculated that Baumanis may have borrowed part of the lyrics from a popular song which was sung to tune of God Save the Queen, modified them and set them to music of his own. Baumanis's lyrics were different from the modern ones: he used the term "Baltics" synonymously and interchangeably with "Latvia" and "Latvians", so "Latvia" was actually mentioned only at the beginning of the first verse. Later the term "Latvia" was removed and replaced with "Baltics" to avoid a ban on the song. This has led to the misapprehension that the term "Latvia" was not part of the song until 1920, when it was chosen as national anthem and the word "Baltics" was replaced with "Latvia".During the annexation of Latvia by the Soviet Union, the singing of "Dievs, svētī Latviju!" was banned. The Soviet republic of Latvia had its own anthem. "Dievs, svētī Latviju!" was restored as the state anthem of Latvia on 15 February 1990, a very short period before Latvian independence was restored.

paragraph_text: Zvārtava Manor (; ) is a manor house in the historical region of Vidzeme, northern Latvia. It was built in 1881 in Tudor Neo-Gothic style.

paragraph_text: VHF Records is an American record label, known for their extensive work with several major experimental artists. The label is based in the Washington, DC suburb of Fairfax, Va., and it initially focused on indie and experimental bands from that region. The label has since branched out to release innovative and offbeat music from around the world, although Northern Virginia artists are still prominently featured in the catalog.

paragraph_text: The First Latvian National Awakening began in the 1850s and continued to bear fruit after World War I when, after two years of struggle in the Latvian War of Independence, Latvia finally won sovereign independence, as recognised by Soviet Russia in 1920 and by the international community in 1921. The Constitution of Latvia was adopted in 1922. Political instability and effects of the Great Depression led to the May 15, 1934 coup d'état by Prime Minister Kārlis Ulmanis. Latvia's independence was interrupted in June -- July 1940, when the country was occupied and incorporated into the Soviet Union. In 1941 it was invaded and occupied by Nazi Germany, then reconquered by the Soviets in 1944 -- 45.

paragraph_text: The Latvian Railway History Museum is a railway museum in Riga, Latvia. It was established on August 30, 1994 and contains more than a thousand items, documents and photographs related to railway communications and signalling equipment, tools and instruments, uniforms and badges.

paragraph_text: Railways must operate at variable speeds. Until the mid 1980s this was only practical with the brush-type DC motor, although such DC can be supplied from an AC catenary via on-board electric power conversion. Since such conversion was not well developed in the late 19th century and early 20th century, most early electrified railways used DC and many still do, particularly rapid transit (subways) and trams. Speed was controlled by connecting the traction motors in various series-parallel combinations, by varying the traction motors' fields, and by inserting and removing starting resistances to limit motor current.

paragraph_text: Ivars Godmanis (born 27 November 1951) is a Latvian politician who was Prime Minister of Latvia from 1990 to 1993 and again from 2007 to 2009. He was the first Prime Minister of Latvia after the country restored its independence from the Soviet Union.

paragraph_text: Operating at normal power line frequencies, universal motors are often found in a range less than 1000 watts. Universal motors also formed the basis of the traditional railway traction motor in electric railways. In this application, the use of AC to power a motor originally designed to run on DC would lead to efficiency losses due to eddy current heating of their magnetic components, particularly the motor field pole-pieces that, for DC, would have used solid (un-laminated) iron and they are now rarely used.

paragraph_text: The outdoor scenes of the film were shot at the Cinevilla backlot in Tukums, Latvia, a backlot built especially for "Defenders of Riga".

paragraph_text: Kilburn High Road railway station is a London Overground station on the London Euston to Watford DC Line near the south end of the Kilburn High Road, London NW6 in the London Borough of Camden.

paragraph_text: Anatols Dinbergs (born Riga, March 3, 1911, died Washington, D.C., November 9, 1993) was one of the preeminent career diplomats of Latvia. He entered service in Latvia's Foreign Ministry in 1932. Dinbergs remained abroad when the Soviet Union occupied Latvia, serving in the Latvian Legation in Washington, D.C., after World War II ended. Dinbergs assumed the highest diplomatic post, that of "chargé d'affaires", in 1970 and represented Latvia's sovereign interests in exile until Latvia reestablished its independence in 1991. As head of the Latvian diplomatic service abroad, Dinbergs was appointed Latvia's first ambassador to the United Nations and subsequently Latvia's first ambassador to the United States. After retirement, he served as Counselor to the Latvian Embassy in Washington, D.C., until his death in 1993.

Question: When did Latvia gain independence from where an experimental 6kV DC railway was built?
Answer: 1920