I have a withdrawn charge for a summary offence (possession of marijuana) from 10 months ago and am wondering if it will show up when I go to Houston in a week or so.

This is what I found at the John Howard Society website...

http://www.johnhoward.ab.ca/pub/A5.htm#Q2

"The names of persons who have been charged but never convicted cannot be accessed from the CPIC database, except in cases in which a discharge has been granted. Even though discharges are not considered convictions, records of discharged offences are maintained by CPIC for a limited time."

And

"Local police create a file for their records, and if the charge is for an indictable or hybrid offence, they may send a copy of this information to the Canadian Police Information Centre (CPIC), managed by the Royal Canadian Mounted Police (RCMP)."

How was it withdrawn? The US border does have access to the CPIC so they WILL see it if it hasn't been removed yet. You need to see for yourself if it has been removed or not. If it hasn't and you attempt to cross, they will see and will PERMANENTLY have you in their system even when it is finally cleared. So you need to find out how long it takes for it to be cleared from the database and double check after it's been removed.