A footnote to the data query at the source explains:

As of December 31, 2001, the transfer of responsibility for sentenced felons from the District of Columbia to the Federal Bureau of Prisons was completed. The District of Columbia no longer operates a prison system and has been excluded from NPS.

The source data file, rather than a "no data" value, continued to report zero for DC after 2001.

In response, we have marked the series as "discontinued" in their metadata and changed periods from 2002 to 2015 to "ND." Figures are quantity of persons (#). The series run from as early as 1977 to 2001.

The series reside in the historical catalog (United States » Demographics » Prisoner Statistics) and include, for example:

• BJSPSJA.DC   = [DISCONTINUED] All Prisoners Under State Jurisdiction: Dist. of Columbia, (#)
• BJSPMYSCA.DC = [DISCONTINUED] Prisoners Sentenced to More Than a Year in Custody of State Correctional Authorities: Dist. of Columbia, (#)
• BJSFSCA.DC   = [DISCONTINUED] Female Prisoners in Custody of State Correctional Authorities: Dist. of Columbia, (#)

Because catalog locations are subject to change, the upper-right search box on DataBuffet.com provide a "find in catalog" mode that accepts a mnemonic