Blair County, Pennsylvania
Demographics
Table:
Historical population

Census	Pop.	Note	%±

1850	21,777	—
1860	27,829	27.8%
1870	38,051	36.7%
1880	52,740	38.6%
1890	70,866	34.4%
1900	85,099	20.1%
1910	108,858	27.9%
1920	128,334	17.9%
1930	139,840	9.0%
1940	140,358	0.4%
1950	139,519	−0.6%
1960	137,270	−1.6%
1970	135,356	−1.4%
1980	136,621	0.9%
1990	130,542	−4.4%
2000	129,144	−1.1%
2010	127,089	−1.6%
2017 (est.)	123,457	[5]	−2.9%
U.S. Decennial Census[6]
1790-1960[7] 1900-1990[8]
1990-2000[9] 2010-2017[2]

Observing the following table concerning 'Blair County, Pennsylvania' in the 'Demographics' section, write a one-sentence description of the highlighted cells and provide it inside the JSON object {"answer": "YOUR ANSWER"}.