When the Bill Emerson Memorial Bridge is dedicated today, Cape Girardeau residents will experience a similar historical moment in time that people in two other Mississippi River towns have shared in the last decade.

The Clark Bridge at Alton, Ill., and the Mark Twain Memorial Bridge in Hannibal, Mo., are the two most recently built bridges spanning the great river between Illinois and Missouri.

Stan Johnson, project engineer for the Cape Girardeau project, first saw the Clark Bridge when he drove across it two months ago. It is also a "cable stay" design.

"The basic design is the same," he said. "But on the Alton bridge, the cables go up from the deck on one side, go through the top of the tower and then continue down to the other half of the deck."

The drive gave him an indication what the first drivers to cross the Emerson Bridge will see.

"But being an engineer, when you're looking at those kind of things, you look at them differently than your average driver," he said. "I tend to notice things like cables and how it all works."

According to www.altonweb.com, the first Clark Bridge cost $1.8 million and opened July 16, 1928. The new bridge was dedicated in January 1994 and cost $118 million. It has more than 160 miles of cable. Its construction was the subject of a a two-hour documentary on PBS.

Hannibal's new Mark Twain Memorial Bridge opened for traffic Sept. 16, 2000. The city's current mayor, Roy Hark, was selling commemorative Pepsi cans depicting the new Twain bridge for the United Way during the dedication ceremony.

"It's been good for us," he said. "Traffic has definitely increased because we went from two to four lanes, and that's given better access to Hannibal. We're growing westward and the new bridge gives a straight shot to the city's expansion. It's helping economic development, though some of the downtown restaurants and gas stations have reported they lost business after it opened."

According to the Hannibal Courier-Post, the original bridge of the same name opened Sept. 4, 1936, and both were designed by the same engineering firm, Sverdrup Civil Inc. of St. Louis, Mo. The two bridges both had a "continuous through truss" design. The two longest spans are the navigation spans, and the other spans are simple truss spans with approaches on either side.

The new Twain bridge's deck has weather sensors to tell maintenance workers what conditions are, including whether the deck is freezing. It also meets interstate regulations because it is Interstate 72. It has 27 piers and four 12-foot-wide travel lanes, 10-foot outside shoulders and 6-foot inside shoulders, and a concrete traffic barrier in the 3-foot wide median.