[2] He was admitted to the bar and entered private practice in Harrisonburg, Rockingham County, Virginia until 1837.

[2] He declined the office of United States Attorney General offered him by President Martin Van Buren and that of Justice of the Supreme Court of Virginia.

[2] Pennybacker received a recess appointment from President Martin Van Buren on April 23, 1839, to a seat on the United States District Court for the Western District of Virginia vacated by Judge Alexander Caldwell.

[2] President James K. Polk named Pennybacker to the very first Board of Regents of the Smithsonian Institution, a group which included Vice-President George M. Dallas, Chief Justice Roger B. Taney, Washington, D.C. Mayor William Winston Seaton, Senator Sidney Breese, United States Representative William Jervis Hough, United States Representative Robert Dale Owen, United States Representative Henry Washington Hilliard, Rufus Choate, Richard Rush, Dr. Benjamin Rush, William C. Preston, Alexander Dallas Bache, and Joseph Gilbert Totten, among others, who met for the first time in September 1846.

[3] Pennybacker was a cousin of Green Berry Samuels, a United States representative from Virginia.