Census Block Groups (1990)

This polygon shapefile shows block groups in the SPC region for the 1990 census. Census block groups are one step above census blocks and are the smallest unit at which the Census Bureau publishes sample data. Block groups typically range from 600 to 3,000 people. Note: Lawrence County was not part of the Southwestern Pennsylvania Commission's region in 1990.本多边形形状文件（shapefile）展示了1990年人口普查中SPC（Southwestern Pennsylvania Commission，宾夕法尼亚州西南部委员会）辖区内的人口普查区块组（census block groups）。人口普查区块组是层级高于人口普查区块（census block）的统计单元，同时也是美国人口普查局（Census Bureau）发布抽样数据的最小统计单元。单个人口普查区块组的人口规模通常介于600至3000人之间。注意：1990年时，劳伦斯县（Lawrence County）并未被纳入宾夕法尼亚州西南部委员会的辖区范围。