Prime Pennants

Bigger isn't always better. "If the size is too large, it can devalue the flag," says Ryan. Many average 15 feet long. To display a U.S. flag in a smaller space, fold the stripes back like an accordion so only a bit of stripe and all the stars show.

TLC. To protect fabric from sunlight and odors, have flags stitched onto an acid-free fabric that's stretched and then framed under UV-protected glass. Use clear acrylic for extremely large flags; glass is too heavy.

Buyer beware. "Dealers claim they occasionally come across forgeries, but that's not the real trouble. "The problem is with collectors who don't recognize what they are getting," says Ryan. "E-bay or an auction house may say it's a valuable 25-star flag, but that doesn't necessarily mean that it's from the 1830s. It may have been made later during the Civil War, when many flags eliminated the stars for Southern states." If making a serious investment, be sure to have a reputable dealer check it out.