[Jim]

Just to add a bit - store them flat in archival quality inert polyester envelopes, but make sure a bit of air can circulate around them. Do not pile them high to create pressure on the photos. Also, keep them in a room where the temperature remains constant and cool, and where the relative humidity remains constant and low. Temperature variations cause the paper to expand and contract, as does humidity variations. Also, high humidity allows mildew and fungus to grow. Spearate out any photos that have fungus or other rot and keep them away from the ones that do not - you do not want it to spread. Be sure to keep them in a place where no insects will come, and where no mice will come either. And keep them out of the sun and only view them in a dim room.

Get them copied digitally since there is nothing you can do to prevent them from eventually disintegrating at some point. To the extent you can have any conserved professionally, focus on the ones for which there are no known duplicates. All WW I era photos are just copies made from negatives - some may be the only copy made or the only one surviving while others may have many known copies and be less tragic if they were lost.