Walpack Township is a township in Sussex County, New Jersey, United States.
 As of the 2010 United States Census, the township had a population of 16, reflecting a decline of 25 (-61.0%) from the 41 counted in the 2000 Census, which had in turn declined by 26 (-38.8%) from the 67 counted in the 1990 Census.
 Walpack Township was one of only four municipalities in New Jersey with a double-digit population as of the 2010 Census, and it placed third behind Tavistock (population 5) and Pine Valley (population 12), both in Camden County.
North Bergen is a township in Hudson County, New Jersey, United States.
 As of the 2010 United States Census, the township had a total population of 60,773, reflecting an increase of 2,681 (+4.6%) from the 58,092 counted in the 2000 Census, which had in turn increased by 9,678 (+20.0%) from the 48,414 counted in the 1990 Census.
 The town was founded in 1843.
 It was much diminished in territory by a series of secessions.
 Situated on the Hudson Palisades, it is one of the "hilliest" municipalities in the United States.
 Like neighboring North Hudson communities, North Bergen is among those places in the nation with the highest population density and a majority Hispanic population.
Elizabeth is both the largest city and the county seat of Union County, in New Jersey, United States.
 As of the 2010 United States Census, the city had a total population of 124,969, retaining its ranking as New Jersey's fourth largest city (by population).
 The population increased by 4,401 (3.7%) from the 120,568 counted in the 2000 Census, which had in turn increased by 10,566 (+9.6%) from the 110,002 counted in the 1990 Census.
 For 2015, the Census Bureau's Population Estimates Program calculated a population of 129,007, an increase of 3.2% from the 2010 enumeration, ranking the city the 210th largest in the nation.
Hope Township is a township in Warren County, New Jersey, United States.
 As of the 2010 United States Census, the township's population was 1,952, reflecting an increase of 61 (+3.2%) from the 1,891 counted in the 2000 Census, which had in turn increased by 172 (+10.0%) from the 1,719 counted in the 1990 Census.
 The 2010 Census population marked the first decennial census in which the township's population exceeded the 1,903 recorded in the 1840 Census, the first recorded population after the township was formed.
Hackettstown is a town in Warren County, New Jersey, United States.
 As of the 2010 United States Census, the town's population was 9,724, reflecting a decline of 679 (-6.5%) from the 10,403 counted in the 2000 Census, which had in turn increased by 2,283 (+28.1%) from the 8,120 counted in the 1990 Census.
 The town is located in the easternmost region of the Lehigh Valley.
Coalwood is an unincorporated community coal town in McDowell County, West Virginia, United States.
 The coal mine in Coalwood reached its peak in the 1960s and finally shut down production on October 1, 1982.
 As of the 1990 Census - the last time the town was counted separately - , the population was 900.
 The town is the setting of the best-selling memoir "October Sky" by Homer Hickam and the movie based on the book.
Dover is a town in Morris County, New Jersey, United States.
 Located on the Rockaway River, Dover is about 31 mi west of New York City and about 23 mi west of Newark, New Jersey.
 As of the 2010 United States Census, the town's population was 18,157, reflecting a decline of 31 (-0.2%) from the 18,188 counted in the 2000 Census, which had in turn increased by 3,073 (+20.3%) from the 15,115 counted in the 1990 Census.
 Dover has become a majority minority community, with nearly 70% of the population as of the 2010 Census identifying themselves as Hispanic, up from 25% in 1980.
Kulumadau is a large, rural non-village (as per the official 1990 Woodlark Island census) on Woodlark Island, Milne Bay Province Papua New Guinea.
 It is served by Guasopa Airport.
 Its population during the 1990 census was 242, though it has since grown extensively; its current population is reported to be about 2,500 people, but there are no official sources for this number, as the last official census was taken in 1990 (this is the case in many rural islands of Milne Bay).
 There is a large primary school in Kulumadau (Kulumadau Primary School), where 200 students are taught (60 coming from outer islands).
 Students must travel to Alotau on the mainland to attend secondary school.
 Kulumadau (along with Guasopa) was built in the post-colonial times, and as such, is not considered a traditional village of Woodlark, however, since its inception, Kulumadau has been the primary population center on Woodlark Island.
Galloway Township is a township in Atlantic County, New Jersey, United States.
 At 115.2 sqmi of total area, Galloway Township is the largest municipality in the State of New Jersey.
 As of the 2010 United States Census, the township's population was 37,349, reflecting an increase of 6,140 (+19.7%) from the 31,209 counted in the 2000 Census, which had in turn increased by 7,879 (+33.8%) from the 23,330 counted in the 1990 Census; The increase of more than 14,000 in population since the 1990 Census was the 11th-highest in the state.
Sky of Stone is the third in a trilogy of memoirs by Homer Hickam, Jr. about his hometown of Coalwood, West Virginia, that began with "October Sky".

Question: What was the population as of the 1990 census of the town about which "Sky of Stone" was written?
Answer: 900