These articles may or may not reference your William.
"The Baltimore Sun" of Monday June 19, 1899, page 7 entitled "Queen Annes Primaries. Lively Scramble Among Democrats for Places on the Ticket."
"The following delegates elected to the nominating convention which will meet on Tuesday: ... ... ... District 7. James E. Higman, Albert Story, H. Clay Hendrix, W. G. Foulks, Samuel A. Wallen."
"The Baltimore Sun" of Thursday May 17, 1900, page 8 entitled "Maryland Notes."
"Constables have been appointed in Queen Anne's county as folllows: S. Carroll Johnson, S. C. Faulkner, W. M. Dunn, T. Frank Seward, Robert Coursey, C. S. Jump, George A. Whiteley, Edgar Hopkins, C. H. Allen, Carroll Vane, Samuel H. Walls, W. R. Coleman and W. G. Foulks."
A dead letter is noted for a Foulks, Wm. in Brooklyn station in "The Baltimore Sun" on January 21, 1901 on page 1.
"The Baltimore Sun" of Sunday November 16 1902, page 7 entitled "Chestertown and Kent County." This references 2 of the children.
"... The friends of Miss Alverda Edwards near Crumpton, Kent county tendered her a surprise party. Those present were Misses Bessie Webb and Anna Melvin, of Washington College, Chestertown; Misses Mary Davis and Ethel Solloway, of Chesterville; Miss Lena Bishop, of Galena; Misses Elsie Woodall, Gussie Walls, Ada Stevens and Anna Foulks, of Crumpton; Messrs. Clever, Spencer Coleman, William P. Foulks, Andrew Woodall, John Jarvis, Harry Talbot, Roy Stafford, Willie Woodall, Joel Clements, Clarence Clark, Wright Coleman, Elwood Coleman and Howard Melvin."
Other similar get-togethers that include Anna and William (Willie) are:
https://www.newspapers.com/image/214608219/ in December 1902
https://www.newspapers.com/image/214411494/ in January 1903
There are also a number of articles that mention a successful pitcher named Foulks, but I did not find a first name so I will not mention that here.
"The Baltimore Sun" of Monday, June 21, 1920, page 5 in a section about fines to drivers includes:
"William Foulks, Cleveland, was fined $40 and costs for exceeding the speed limit and for going past a car moving in the same direction on the right side instead of the left."
It's not much, but maybe there's a clue here for you.