Series 251 Court of General Session, 1768-1857 (gaps)
Series 252 New York City Watershed Proceedings, 1877-1917
Series 253 District Attorney Case Files, 1892-1949 (bulk 1906-1949)
Series 254 Bronx River Parkway Reservation, Historic American Engineering Record, 2001-2002
Series 255 Bronx River Parkway Plans, 1915-1920
Series 256 County Office Building Plans, 1968-1974
Series 257 Circuit Court, 1796-1888 (gaps)
Series 258 Justice Court, 1786-1898 (gaps)
Series 259 Court of Special Sessions 1812, 1828, 1841-1879, 1889-1890
Series 260 County Court, 1823-1870 (gaps)
Series 261 Court of Special Sessions – Miscellaneous, 1832-1846, 1859-1860, 1891, 1908, 1912
Series 262 Miscellaneous Courts – Petit Jurors, 1836-1869 (gaps)
Series 263 Index to Lis Pendens, 1826-1902
Series 264 Photographic Indexes, ca. 1912-1932
Series 265 Election and Canvass Records, 1826
Series 266 Coroner’s Inquest Records, 1805, 1808, 1823-1829, 1832-1843 (gaps), 1853, 1874, 1897, 1905, 1909, 1911
Series 267 Building Plans -- Archives and Records Center, 1988-1990, 2012
Series 268 Westchester County Control Survey Records, Department of Public Works Files, ca. 1930s-early 1950s
Series 269 Office for Women, 1980-1995
Series 270 Airport Subject Files, Commissioner of Public Works, 1944-1977
Series 271 Miscellaneous Records, "Register's Office," 1857-1910
Series 272 Returns of Births, Marriages, and Deaths, 1842, 1847-1848 (bulk 1847)
Series 273 Office for the Disabled Records, 1975-1995
Series 274 Department of Consumer Affairs, Weights and Measures Publicity Clippings, 1960-1990 (bulk 1973-1990)
Series 275 Westchester 2000, 1971-1998
Series 276 Acquisition & Contract -- Airport Agreements, 1942-1978
Series 277 Blue Mountain Reservation -- Reports and Photographs, 1933-1936
Series 278 Internal Archives Collection
Series 279 Incorporation Records -- Originals -- "Liber 1", 1848-1909 (bulk 1848-1890)
Series 280 Parks Department Contracts and Agreements, 1922-1972 (bulk 1922-1954, 1962-1968)
Series 281 Westchester 2000 -- Sal Prezioso Collection, 1957-1997 (bulk 1984-1988)
Series 282 Discharge of Mortgages, 1829-1853
Series 283 Public Works Vehicle Safety Program Slide Collection, c.1978-1990
Series 284 Mount Vernon Board of Health Minutes, 1881-1945, 1968-1970
Series 285 Department of Public Safety "In Memoriam" Collection, 1792, 1925-1985
Series 286 Sheriff Darius Lyon Receipt Book, 1865-1871, 1888
Series 287 Naturalization Repatriation Proceedings, 1937-1967 (bulk 1941-1942)
Series 288 Naturalization Witness Depositions, 1910-1960
Series 289 County Historian Files, 1987-1995
Series 290 Naturalizations -- Transfers, 1953-1991
Series 291 Naturalizations -- Court Calendars, 1907-1915
Series 292 Corporation Registers, 1885-1929
Series 293 County Historian Videotape Collection, 1984-1994
Series 294 WPA Veterans' Cemetery Survey Forms - Photocopies, 1928-1938
Series 295 Supreme Court Cases Index, 1847-1924
Series 296 Index to Special Proceedings, 1817-1934
Series 297 Supreme Court Cases, 1847-1911
Series 298 Research Articles Based on the Collections of the Westchester County Archives, 1987-2011
Series 299 Board of Supervisors Board Meeting Packets, 1925-1929 (gaps); 1930-1969
Series 300 Board of Supervisor / Board of Legislators Subject Files, 1890-1980 (bulk 1928-1969)