Exhibit 99.1



                                                                    June 1, 1998

ARCH COAL COMPLETES ACQUISITION OF
ATLANTIC RICHFIELD'S DOMESTIC COAL OPERATIONS

      St. Louis,  MO -- Arch Coal, Inc.  (NYSE:ACI)  announced today that it has
completed the acquisition of Atlantic  Richfield's  domestic coal operations for
approximately $1.14 billion. The transaction makes Arch Coal the nation's second
largest  coal  producer  with  expected  coal sales of nearly 110  million  tons
annually,   annual  revenues  of  about  $2  billion,  and  a  reserve  base  of
approximately 3.4 billion tons.

      "We believe this transaction will create  substantial  long-term value for
our shareholders,"  said Steven F. Leer,  president and chief executive officer.
"With the  addition  of the ARCO  properties,  we can now supply a wide range of
coal products in a  cost-competitive  manner to virtually every major coal-fired
power plant in the United States."

      "We will now turn our full attention to  integrating  these new operations
into Arch  Coal,"  Leer  added.  "We have a strong  track  record of  successful
integration efforts and a great deal of experience operating large-scale surface
and longwall mines such as those we have just acquired. Furthermore, the men and
women at these  mines  have  demonstrated  that  they  share our  commitment  to
operating in a safe, highly productive and  environmentally  responsible manner.
For these reasons, we expect a quick and efficient integration process."

      The completion of the transaction  creates a new joint venture called Arch
Western  Resources,  LLC. Arch Western Resources is comprised of the former ARCO
Coal Company  properties  in Wyoming,  Colorado and Utah,  as well as properties
Arch Coal owned and operated in southern Wyoming. Arch has a 99% interest in the
new joint  venture  and ARCO has a 1%  interest.  Arch  Western  Resources  will
account for all of Arch Coal's operating activity west of the Mississippi River.

      The  transaction  will be  financed  entirely  with debt  using new credit
facilities that became effective today. As part of these new credit  facilities,
Arch Coal terminated its existing  credit  facilities and redeemed $35.7 million
in senior  notes.  The  termination  of these  agreements  will result in a $2.4
million pre-tax charge in the second quarter of 1998.


                        


      "One great  strength  of the  expanded  company is its ability to generate
strong  levels of cash flow," Leer said.  "We plan to use free cash flow both to
fund additional growth and to pay down debt in a steady and aggressive fashion."
In 1997 on a pro forma  combined  basis,  Arch  Coal and  ARCO's  domestic  coal
operations  generated more than $400 million in earnings from operations  before
the  effects  of  changes  in  accounting  principles,   non-recurring  charges,
interest, taxes, depreciation, depletion and amortization (EBITDA).

      EBITDA is presented because it is a widely accepted financial indicator of
a company's  ability to incur and service debt.  EBITDA should not be considered
in isolation or as an alternative to net income,  operating  income,  cash flows
from  operations  or as a measure of a  company's  profitability,  liquidity  or
performance  under generally  accepted  accounting  principles.  Certain matters
discussed within this press release are  forward-looking  statements  within the
meaning of the Private Securities  Litigation Reform Act of 1995.  Although Arch
Coal,  Inc.  believes  the  expectations   reflected  in  such   forward-looking
statements  are based on reasonable  assumptions,  it can give no assurance that
its  expectations  will be attained.  Factors that could cause actual results to
differ materially from expectations  include financial  performance,  changes in
local or national  economic  conditions,  and other risks  detailed from time to
time in the Company's  SEC reports,  including  quarterly  reports on Form 10-Q,
reports on Form 8-K, and annual reports on Form 10-K.

      Arch Coal is the nation's  second  largest coal producer  with  subsidiary
operations in West Virginia, Kentucky, Virginia, Illinois, Wyoming, Colorado and
Utah. Through these operations, Arch Coal provides the fuel for approximately 6%
of the nation's electric power generation.