Legally, what happens to a trademark after a company goes defunct? Are the rights still owned or can someone else use it (lawsuit, register)

[Onslow]

For example:

Circuit City was unable to weather the Great Recession of 2008 and went under.

HQ Hardware was unable to continue to compete with Home Depot and Lowes and closed it's last stores in 1999.

So, could I legally open an electronics store and call it Circuit City, or a hardware store and call it HQ, and benefit from the name recognition?

Or does the original owner retain it beyond the existence of the company?

[Rabrrita]

It's retained by whomever owns the trademark for as long as they continue re registering it. Circuit City's trademark is still in existence and I believe is currently owned by Ronny Shmoel. Even when the trademark was not being publicly used, Tiger Direct would sue anyone who used it when they owned the rights to the CC trademark. There is plans to restart Circuit City brand under a new format, so, using the name most certainly will result in a lawsuit.

[freemkt]

You can look up trademarks online. There's a simple text search if you don't need to look up "design marks".

The same (text) trademark can be used by different owners for different unrelated products, e.g. Domino's Pizza and Domino Sugar are sufficiently different that reasonable individuals do not confuse the two.

If you do an online trademark search, you'll see that there are many more DEAD abandoned trademarks than LIVE trademarks.

Trademark Electronic Search System (TESS)

[cpg35223]

There are live marks and dead ones.

[oregonwoodsmoke]

What happens if you want to use it is you offer to buy it. Either you agree on a price or they don't want to sell.

The same goes for their domain name. You can offer to buy it from them.