The next big thing on TV may turn out to be a very old idea: westerns.

Pretty much banished from prime time for more than 20 years, two major series based on the old West are quietly being prepared for next year.

ABC is pushing ahead with a series called Then Came Jones -- set in El Paso, Texas at the turn of the century, about a former-outlaw-turned-sheriff Ben Jones (Sean Patrick Flannery of The Adventures of Young Indiana Jones).

Melissa Gilbert, who starred as a little girl in the western-oriented Little House on the Prairie, was hired this week to star as Flannery's sister, according to several trade reports.

And when HBO went looking for a new series, it too settled on a western -- Deadwood which was created by Hill Street Blues writer and NYPD Blue co-creator David Milch.

The HBO series is set in the Wild West town of Deadwood, S.D. two weeks after the Battle of Little Bighorn in June 1876.

The showwill incorporate historical figures such as Wild Bill Hickock and Calamity Jane along with a roster of fictional characters, according to published reports.

"I think it's an interesting extension of the post-9/11 development world," says industry analyst Stacey Lynn Koerner of Initiative Media.

"A lot of programming [since Sept. 11] has been very family-oriented . . . [westerns] are a different kind of Americana and are a way to celebrate our heritage and our history.

"And westerns as a genre have a great ability to tell a story."

Anyone over the age of 30 remembers a time when westerns were a major ingredient of every network's lineup. Shows like Gunsmoke, Bonanza, Bat Masterson, Rawhide, The Wild, Wild West and Maverick were staples.

Around the Vietnam era, westerns went out of fashion.

So why the sudden resurgence?

"If you look at the PBS [reality show] Frontier House, it was very well-received," says Koerner.

"I think there's a whole idea that maybe we need to retrace our steps back to simpler times and go back to what's really important."

For more news, entertainment and sports coverage, click here for NYPost.com.