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A good scholarly site for all sorts of eldritch, cyclopean, cosmic horrors is www.hplovecraft.com. It's completely noncommercial, and includes links to bibliographies, TV shows, and art. Even though the site maintainer thinks the monsters get too much attention, it describes most of them as well.
I-210 (numbered as another interstate) Alabama
This is the original number approved for a proposed highway connecting I-65 to I-10 in Mobile. The 6.25-mile project was conceived decades ago; Alabama requested federal interstate funding in 1958. 
In 1980, the project was approved as Interstate 210. However, as public hearings and studies continued, local opposition helped stop the highway just short of I-10.  One of the early I-210 alternatives, a spur from I-65 ending at Bauregard Street, was selected instead; , and in 1987, the highway was renumbered I-165.  It opened in 1996.
Though I-210/165 never reached I-10, an interchange was constructed there, just west of the George Wallace Tunnel. It is now used for Exit 26, Water Street, leading to US 43 and downtown Mobile. 
See also: Interstate 210 - Alabama (aaroads; photos detailed history of I-210 alternatives)
48.72 miles ; Foothill Freeway; from I-5 in Sylmar to I-10 near Pomona. I-210 was approved as a chargeable interstate on Sept. 15, 1955.   The first segment opened in 1955; the last, in 1981. In the early 1970s, completed portions were co-signed with CA 118, which went through the area. 
I-210 is currently being rerouted and extended to I-10 in Redlands. The short north-south segment between Glendora (the "elbow") and I-10 near Pomona has already been redesignated as a northern extension of CA 57.
Michigan had similar ideas around Detroit
When the number for this route was being decided (in the 1950s), California suggested "Interstate 12," then "Interstate 14." 
A 5.4 mile gap of I-210 had been delayed because of a habitat of red-nosed frogs; after it flooded out, however, the go-ahead was given to complete the freeway. 
Extending I-210: Introduction
Interstate 210 will be extended almost 30 miles to I-10 in Redlands, east of San Bernardino, I-15, and I-215. About half of the new highway is open to traffic and marked CA 210. The extension will probably be designated I-210, but not until all segments are complete (in 2007). The freeway will be 8 lanes wide including 2 HOV lanes.
Putting it together
The 210 extension consists of the following segments, moving west to east:
Extending I-210: Background
The full Foothill Freeway was first conceived in 1948,  and it was added to the state's planned freeway system in 1959. In 1968, California petitioned AASHTO to add an interstate between I-210 at San Dimas to I-15 at Fontana, but this was denied.  The freeway extension received funding in 1989. 
In February 1998, State proposal AB 2388 called for eliminating CA 30 and extending 210 about 28 miles along 30's path to cross I-15 and reach I-10 in Redlands.  In November 1998, California petitioned AASHTO to reroute the I-210 designation in the same manner; but AASHTO "deferred action" on that proposal, as it was unknown if the state had also asked FHWA to add the route to the interstate system. 
In July 1999, a bill was approved creating a CA 210 designation from Glendora (the eastern "elbow" in I-210) to San Bernardino. This replaces the short section of existing CA 30 freeway at I-210, and incorporates new mileage under construction. The portion of I-210 south of the 210 elbow would be reassigned to CA 57.  On April 16, 1999, California resubmitted the I-210 proposal to AASHTO, but then withdrew it. 
Easy on, easy off
An unfortunate side effect of the 210 extension is (as of January 2003) in increase in bank robberies in the area: gang members from Los Angeles are reported to have robbed several banks there, as the nearby 210 offers a quick getaway. Some detectives have nicknamed the freeway the "211", based on the penal code number for armed robbery. 
12.40 miles ; serves Lake Charles, looping south of I-10. Completed around 1980.