|Rank|Name|Height|Floors|Year|Notes|
|---|---|---|---|---|---|
|1|Zions Bank Building     Zions Bank Building in Downtown Boise, Idaho|323 ft (98 m)|20|2013|Tallest building in state since 2013.|
|2|Boise Airport Air Traffic Control Tower|295 ft (90 m)||2009|Tallest ATC tower in the Northwest.|
|3|US Bank Plaza     US Bank Building in Downtown Boise|267 ft (81 m)|19|1978|Tallest building in state from 1978 to 2013. "Idaho First Plaza" until 1989.|
|3|One Capital Center     One Capital Center in Downtown Boise, Idaho|206 ft (63 m)|14|1975|Tallest building in Boise from 1975 to 1978.|
|4|Idaho State Capitol     Idaho State Capitol; Boise, Idaho|198 ft (60 m)|4|1920|Tallest building in Boise from 1920 to 1975.|
|5|The Grove Hotel     Grove Hotel in Downtown Boise, Idaho|196 ft (60 m)|16|2000||
|6|The Aspen     Aspen Loft Building in Downtown Boise, Idaho|194 ft (59 m)|17|2009||
|7|Wells Fargo Building     Wells Fargo Building in Downtown Boise, Idaho|182 ft (55 m)|11|1988|First Interstate until 1996|
|8|Banner Bank Building     Banner Bank Building in Downtown Boise, Idaho|181 ft (55 m)|11|2006||
|9|Key Tower     Key Bank Building in Downtown Boise, Idaho|174 ft (53 m)|13|1963|Bank of Idaho until 1981, First Interstate until 1988|
|10|Bronco Stadium     Bronco stadium in Boise, Idaho|170 ft (52 m)||1970||
|11|Hoff Building     Hoff Building in Downtown Boise, Idaho|165 ft (50 m)|14|1930||
|12|Chase Tower Plaza     Chase Building in Downtown Boise, Idaho|160 ft (49 m)|11|1995|Washington Mutual until 2009|
|13|Idaho Power Building     Idaho Power Building in Downtown Boise, Idaho|160 ft (49 m)|9|1990||

Question: what is the number of floors of the oldest building?
Answer: 4