Text of the plaque is below.

THIS TABLET RECORDS THE FACT THAT THE
FOLLOWING TROOPS WERE QUARTERED IN THE
UNITED STATES CAPITOL IN RESPONSE TO
PRESIDENT LINCOLN'S CALL FOR VOLUNTEERS
*** APRIL 15, 1861 ***

MASSACHUSETTS
SIXTH REGIMENT OF MASSACHUSETTS
EIGHTH REGIMENT OF MASSACHUSETTS
FIFTH REGIMENT OF MASSACHUSETTS

NEW YORK
SEVENTH REGIMENT (NEW YORK STATE MILITIA)
ELLSWORTH'S FIRE ZOUAVES (ELEVENTH NEW YORK REGIMENT)
SEVENTY-FIRST REGIMENT
FIFTH NEW YORK REGIMENT

PENNSYLVANIA
LOGAN GUARDS OF LEWISTOWN
THE WASHINGTON ARTILLERISTS OF POTTSVILLE
THE NATIONAL LIGHT INFANTRY OF POTTSVILLE
THE ALLEN INFANTRY RIFLES OF ALLENTOWN
THE RINGGOLD LIGHT ARTILLERY OF READING
THE SEVENTEETH REGIMENT OF
PENNSYLVANIA VOLUNTEER INFANTRY

DISTRICT OF COLUMBIA
COMPANIES E.A.C. AND F (NATIONAL GUARD)
MECHANICS' UNION RIFLES

Authorized by 88th Congress of the United States – August 17, 1964