Trailer storage place North/Northwest/Northeast of Washington DC?

[egraham]

Can you recommend a trailer storage place North/Northwest/Northeast of Washington DC?

We live in Alexandria VA, just across the river from Washington, D.C., and cannot store our trailer at our house. As most of our trips will find us heading north/northwest/northeast (NOT south on the I-95), we are hoping to find a trailer storage place in those general directions, within an hour of Alexandria.
Ideally, it would have a locking, coded entry and 23-hour access.

Thanks for your help.