The short version is that it is indicating that someone in the city founders' family history was an illegitimate son of a member of the royal family. The long version is below. :) Enjoy. It's a "baton sinister." In heraldry the term sinister means 'left' - as far as positioning goes, towards the viewer's right. Keep in mind that heraldic directions are specified from the shieldbearer's point of view. For example, if a beast is facing towards the right, it is described as sinister. The opposite of sinister is dexter. Here's a good definition - "In heraldry, the baton is an ordinary in the shape of a thin diagonal line starting in the dexter chief, but not reaching the edges of the device. It is a diminutive of the bend. If the baton starts in the sinister chief, it is called a baton sinister. By the 17th century a baton sinister was also used to indicate illegitimacy (cf. abatement). This usage is also mentioned as being used in Burgundy in 1463." (http://cunnan.sca.org.au/wiki/Main_Page) It's interesting that "Fitzroy" the name actually began its meaning as fitz-royal - or the illegitimate son of royalty. Here's the Webster's definition: "Webster's Revised Unabridged Dictionary - Fitz Fitz, n. [OF. fils, filz, fiz, son, F. fils, L. filius. See Filial.] A son; -- used in compound names, to indicate paternity, esp. of the illegitimate sons of kings and princes of the blood; as, Fitzroy, the son of the king; Fitzclarence, the son of the duke of Clarence."

In heraldry, a "Bend" is a colored band that runs from the upper left (as seen by the viewer) corner of the shield to the lower right. YOUR question refers to a "bend sinister." A bend sinister is a bend which runs from the upper right (as seen by the viewer) corner of the shield to the lower left. (http://en.wikipedia.org/wiki/Bend_%28heraldry%29) (In Latin, left is sinister, right is dexter.) At http://www.fleurdelis.com/meanings.htm and at http://www.irishsurnames.com/shields.htm there is a symbol going the opposite direction (lower right to upper left) called a "Bend" or "Bendy." It signifies "defense" or "protection," which would make sense for a city's coat of arms. An earlier Answerbag question about the same thing was answered this way: It can be a scarf or shield suspender of a knight commander. It means defence or protection. (http://www.answerbag.com/q_view/46788)